Questions of HC Varma class 10th (chapter wise)

 Reflection of Light

A. Very-Short-Answer Questions

1. From which surface of a mirror-the polished surface or the silvered surface-does most of the light reflect?

2. In which kinds of mirrors-plane, concave or Convex can you get a virtual image of an object placed in front of it?

3. What is the principal axis of a spherical mirror?

4. A concave mirror forms a real image of the same size as that of the object. Where is the object placed?

5. Can a convex mirror form a real image of an object?

6. A ray ACB is incident on a spherical mirror whose center of curvature is C. In which direction will it reflect?

7. What is the sign of the object-distance u when an object is placed before a concave mirror?

8. Where can the position of an object be if a concave mirror forms its erect and virtual image?

9. A mirror has focal length f = +10 cm. Is it convex or concave?

10. What are the values of the angle of incidence and the angle of reflection for normal incidence on a plane mirror? (2005)

11. In the diagram, the ray is incident parallel to the principal axis. Redraw the diagram, showing the reflected ray. (2006)

Fig. 1.E1

B. Short-Answer Questions

1. What is silvering of a mirror?

2. Write the two laws of reflection of light.

3. What do you understand by the radius of curvature of a spherical mirror?

4. What is the difference between a real image and a virtual image?

5. Draw a diagram showing the pole, focus, center of curvature and principal axis of a concave mirror.

6. Convex mirrors are used as rear-view mirrors in scooters, motorcycles, etc. Explain why.

7. Draw ray diagrams to show the formation of images when an object is placed (a) between the pole and focus, and (b) between the center of curvature and focus. (2004)

C. Long-Answer Questions

1. Describe a method to measure the focal length of a Concave mirror.

2. Write the sign convention used for spherical mirrors.

3. By drawing a neat ray diagram, show the formation of the image of a point object placed above the principal axis of a convex mirror. Explain the construction.

D. Numerical Problems

1. An object is placed at a distance of 12 cm from a concave mirror of radius of curvature 16 cm. Find the position of the image.

2. An object of height 2 cm is placed at a distance of 15 cm from a concave mirror of focal length 10 cm. Draw a scale diagram to locate the image. From the diagram, find the length of the image formed.

3. The image of an object placed 16 cm from a concave mirror is formed at a distance of 24 cm from the mirror. Calculate the possible focal lengths of the concave mirror from this information.

4. An object is placed 20 cm from a convex mirror. Its image is formed 12 cm from the mirror. Find the focal length of the mirror.

5. Find the position, size and nature of the image formed by a spherical mirror from the following data.

f =-12 cm,

u =-36 cm,

h_o=2 cm

6. An object is placed at a distance of 12 cm from a concave mirror. The image formed is real and four times larger that the object. Calculate the distance of the image from the mirror. (2006)

7. An object is placed 24 cm from a concave mirror. Its image is inverted and double the size of the object. Find the focal length of the mirror and the position where the image is formed.

8. Where should an object be placed before a concave mirror of focal length 20 cm so that a real image is formed at a distance of 60 cm from it?

9. An object is placed at a distance of 12 cm from a convex mirror of radius of curvature 12 cm. Find the position of the image.

10 If the height of the object in the previous problem is 1.2 cm, what will be the height of the image?

11. When a concave mirror is placed facing the sun, the sun's rays converge to a point 10 cm from the mirror. Now, an erect, 2-Cm-long pin is placed 15 cm away on the principal axis of the mirror. If you want to get the image of the pin on a card, where would you place the card? What would be the nature and height of the image?

E. Objective Questions 

I. Pick the correct option.

1. A mirror forms a virtual image of a real object.

(a) It must be a convex mirror.

(b) It must be a concave mirror.

(C)It must be a plane mirror.

(d) It may be any of the mirrors mentioned above.

2. The angle of incidence is the angle between

(a) the incident ray and the surface of the mirror

(b) the reflected ray and the surface of the mirror

(C) the normal to the surface and the incident ray

(d) the normal to the surface and the reflected ray

3. The angle of reflection is the angle between

(a) the incident ray and the surface of the mirror

(b) the reflected ray and the surface of the mirror

(C) the normal to the surface and the incident ray

(d) the normal to the surface and the reflected ray

4. An object is placed at the Centre of curvature of a Concave mirror. The distance between its image and the pole is

(a) equal to f

(b) between f and 2f

(c)equal to 2f

(d) greater than 2f

5. An object of size 2.0 cm is placed perpendicular to the principal axis of a concave mirror. The distance of the object from the mirror equals the radius of Curvature. The size of the image will be

(a) 0.5 cm

(b) 1.0 cm

(c) 1.5 cm

(d) 2.0 cm

6, The magnification m of an image formed by a spherical mirror is negative. It means, the image is

(a) smaller than the object

(b) larger than the object

(c) erect

(d) inverted

7. A point object is placed on the principal axis of a spherical mirror. The object-distance u is

(a) definitely negative

(b) definitely positive

(c) positive if the object is to the left of the Centre of curvature

(d) positive if the object is to the right of the Centre of curvature

8. f = r/2 is valid

(a) for convex mirrors but not for concave mirrors

(b) for concave mirrors but not for convex mirrors

(c) for both convex and concave mirrors

(d) neither for convex mirrors nor for concave mirrors

9. A ray of light is incident on a concave mirror. If it is parallel to the principal axis, the reflected ray will

(a) pass through the focus

(b) pass through the Centre of curvature

(c) pass through the pole

(d) retrace its path

10. If an incident ray passes through the Centre of curvature of a spherical mirror, the reflected ray will

(a) pass through the pole

(b) pass through the focus

(c) retrace its path

(d) be parallel to the principal axis

11. To get an image larger than the object, one can use

(a) a convex mirror but nota concave mirror

(b) a concave mirror but not a convex mirror

(c) either a convex mirror or a concave mirror

(d) a plane mirror

II. Mark the statements True (T) or False (F).

1. Light cannot travel in vacuum.

2. No particle can ever move at a speed greater than that of light in vacuum.

3. The angle of incidence is equal to the angle of reflection. This is true for reflection from plane mirrors, but is not true for reflection from spherical mirrors.

4. The focal length of a spherical mirror has a smaller magnitude than that of its radius of curvature.

5. A spherical mirror never forms an image whose size is the same as that of the object.

6. A ray starting from the focus of a concave mirror becomes parallel to the principal axis after reflection.

7. The mirror equation is valid only if the aperture of the mirror is small.

8. A real image of a point object can be formed only by a concave mirror.

9. A ray of light incident parallel to the principal axis of a spherical mirror retraces its path after reflection.

Refraction of light

A. Very-Short-Answer Questions

1. Define refractive index.

2. When a ray of light passes from Medium 1 to Medium 2, it bends away from the normal. Which of the two is the optically denser medium?

3. A ray of light travelling in air is incident on a face of a rectangular slab and comes out from the opposite face. The angle between the incident ray and the normal to the surface is 30°. What is the angle between the ray coming out of the slab and the normal to the face from which it comes out?

4. How should a ray be incident on a rectangular slab so that it comes out from the opposite side without being displaced?

5. Define the principal axis of a lens.

6. Where should an object be placed before a convex lens so that a real image of the same size as the object is formed?

7. Where should a pin be placed before a convex lens so that the image formed is at infinity?

8. The focal length of a thin lens is given by f =-10 cm. Is the lens concave or convex?

9. The power of a lens used in the reading glasses of a person is +1.5 D. Is the lens concave or convex?

10. When an object is placed before a lens, the lens forms a virtual image for all positions of the object. Is the lens convex or concave?

11. A lens forms an erect image for all positions of an object in front of it. Is the lens convex or concave?

12. Write the relation between u, v and f of a thin lens.

13. Name the muscles responsible for the focusing mechanism of the eye.

14. Name the sense receptors found on the retina of the eye.

15. Define the following in one sentence each.

(a) Near point of the eye

(b) Far point of the eye

(c) Least distance of distinct vision

(d) Accommodation

16. Name two common defects of the eye.

17. What kind of lens should be given to a person suffering from near-sightedness (myopia)?

18. A person has concave lenses in his spectacles. Which defect of vision is he suffering from?

19. Which kind of lens is used to correct long-sightedness (hypermetropia)?

20. A student sitting at the back of a class is not able to see what is written on the blackboard. What defect of vision is he suffering from? Which lens (convex or concave) should be used to correct the defect?

21. What is the main advantage of a contact lens over

spectacles?

B. Short-Answer Questions

1. Write Snell's law, explaining the meaning of the symbols used.

2. What is a thin lens? What is the difference in construction between a convex and a concave lens?

3. Why is a convex lens called a converging lens and a concave lens, a diverging lens?

4. How do you conclude that a ray of light incident towards the optical center of a thin lens is transmitted almost without any deviation?

5. The focal length of a convex lens is f. How does the size of the image placed in front of it changes as the object is brought progressively closer to the focus from a distance which is just greater than 2f?

6. Assuming the principal axis as the x-axis and the optical center as the origin, how will you determine the signs of the quantities u, v and f for a lens?

7. Draw a neat diagram of the human eye and indicate its main parts.

8. How does the eye control the amount of light entering it?

9. What is the blind spot of the eye?

10. Why can you not see an object clearly if it is placed

very close to your eyes?

11. Why do planets not appear to twinkle like stars?

C. Long-Answer Questions

1. An extended object is placed perpendicular to the principal axis of a convex lens. Draw neat diagrams to show the image formation in the following cases. (a) The object is at a distance that is more than double the focal length of the lens. (b) The object is at a distance equal to double the focal length. (c) The object is at a distance that is more than its focal length but is less than double the focal length.

2. Describe a method to measure the focal length of a Convex lens.

3. Explain the process of accommodation in the human eye.

4. What is myopia (near-sightedness)? Explain with a ray diagram how it can be corrected using a lens.

5. What is hypermetropia (far-sightedness)? Write two causes for the development of this defect. Explain how it can be corrected using a lens. (2005, '06)

6. Describe briefly why stars twinkle.

7. Why does the sun become visible even before it actually rises above the horizon at sunrise?

D. Numerical Problems

1. The refractive indices of water and glass are 4/3 and 3/2 respectively. Find the speed of light in each. (Similar, 2005)

2. A ray of light travelling in air falls on the surface of a transparent material at an angle of 45° to the normal. It bends by 15° after refraction. Find the refractive index of the material.

3. A ray of light travelling in air is incident on the surface of a plastic slab at an angle. If the angle of refraction is 30°, and the refractive index of the plastic is V3, find the angle of incidence.

4. Light is incident on a clear-plastic block at an angle of 45°. The speed of light in the plastic is c/W2, where c is the speed of light in vacuum. Find the angle of refraction.

5. Find the refractive index of air with respect to water (n_water=4/3).

6. A diamond (n = 2.42) is dipped in a liquid of refractive index 1.4. Find the refractive index of diamond with respect to the liquid.

7. An object is placed at a distance of 30cm from a convex lens of focal length 20 cm.

(a) Find the position of the image.

(b) Is the image real or virtual?

(c) Is the image erect or inverted?

8. A1.0-cm-high object is placed at a distance of 12 cm from a convex lens of focal length 16 cm.

(a) Find the position of the image.

(b) Is the image real or virtual?

(c) Find the size of the image.

(d) Is the image erect or inverted? (Similar, 2004)

9. A 2.0-cm-high object is placed 12 cm from a convex lens, perpendicular to its principal axis. The lens forms a real image, whose size is 1.5 cm. Find the power of the lens.

10. An object is placed at a distance of 10 cm from a concave lens of focal length 20 cm. Find the position of the image and discuss its nature.

11. A 3.5-cm-high object is placed at a distance of 12 cm from a concave lens of focal length 16 cm. Find the size of the image.

12. An object is placed at a distance of 50 cm from a concave lens. The image is formed at a distance of 20 cm from the lens. Find the focal length of the lens.

13. An object is placed before a concave lens of focal length 12 cm. The size of the image formed by the lens is half the size of the object. Calculate the distance of the object from the lens.

14. What is the power of a concave lens of focal length 50 cm?

15. A convex lens of focal length 18 cm and a concave lens of focal length 24 cm are placed in contactsu that they have a common principal axis. will the comblnation act as a convex lens or a concave lens rind the focal length and power of the combination.

16. The far point of a person suffering from myopla 15 -metres from the eye. Find the focal length and power of the corrective lens that will correct his vision.

17. The near point of an elderly person is 50 cm from the eye. Find the focal length and power ot the Corrective lens that will correct his vision.

E. Objective Questions

I. Pick the correct option.

1. A ray of light travelling in air falls obliquely on the Surface of a calm pond. It Will

(a) go into the water without deviating from its path

(b) deviate away rom the normal

(C) deviate towards the normal

(d) turn back on its original path

2. A ray of light goes from a medium of refractive index m to a medium of refractive index n2. The angle of incidence isi and the angle of refraction isr. Then, sin i/ sin r is equal too

(a) n₁

(b) n₂

(C) n₁,/n₂ 

(d) n₂/n₁

3. A thin lens and a spherical mirror have a focal length of +15 cm each.

(a) Both are convex.

(b) The lens is convex and the mirror is concave.

(C) The lens is concave and the mirror is convex.

(d) Both are concave.

4. A convex lens

(a) is thicker at the middle than at the edges

(b) is thicker at the edges than at the middle

(c) has uniform thickness everywhere

(d) is called a diverging lens

5. A convex lens forms a Virtual image when an object is placed at a distance of 18 cm from it. The focal length must be

(a) greater than 36 cm

(c) less than 36 cm

(b) greater than 18 cm

(d) less than 18 cm

6. An object is placed before a convex lens. The image formed

(a) is always real

(C) is always virtual

(b) may be real or virtual

(d) is always erect

7. An object is placed before a concave lens. The image formed

(a) is always erect

(b) may be erect or inverted

(C) is always inverted

(d) is always real

8. A lens has a power of +0.5 D. It is

(a) a concave lens of focal length 5 m

(b) a convex lens of focal length 5 cm

(c) a convex lens of focal length 2 m

(d) a concave lens of focal length 2 m

9. A parallel beam of light falling on the eye gets focused on the retina because of refractions at

(a) the cornea

(b) the crystalline lens

(c) the vitreous humor

(d) various surtaces in the eye

10. The combination responsible for admitting different amounts of light into the eye is

(a) ciliary muscles and crystalline lens

(b) ciliary muscles and pupil

(C) iris and pupil

(d) rods and cones

11. The muscles of the iris control the

(a) focal length of the eye-lens

(6) opening of the pupil

(c) shape of the crystalline ens

(d) optiC nerve

12. When the eye is focused on an object very far away, the focal length of the eye-lens is

(a) maximum

(b) minimum

(c) equal to that of the crystalline lens

(d) halt its maximum focal length

13. Other names for myOpia are

(a) hyperopia and hypermetropia

(b) long-sightedness and hyperopia

(c) near-sightedness and presbyopia

(d) near-sightedness and short-sightedness

14. The inability among the elderly to see nearby objects clearly because of the weakening of the ciliary muscles is called

(a) far-sightedness

(c) presbyopia

(b) near-sightedness

(d) myop1a

II. Mark the statements True (T) or False (F).

1. When a ray of light passes from an optically denser medium to a rarer medium, it slows down.

2. If a ray of light passes from vacuum to a transparent medium, it will bend away from the normal.

3. The central portion of a thin lens behaves like a rectangular slab.

4. The values of f and u for a concave lens are always negative by convention.

5. When two lenses are placed in contact, the focal length of the combination is equal to the sum of the focal lengths of the lenses.

6. The number of cones in the human eye is more than the number of rods.

7. When light rays are incident on the eye, maximum deviation takes place at the cornea.

8. For the myopic eye, the far point is farther away than normal.

Dispersion and Scattering of light

A. Very-Short-Answer Questions

1. Which is responsible for dispersion of ight reflection or refraction?

2. Define dispersion.

3. Name the component of white light that deviates the least and the component that deviates the most while passing through a glass prism.

4. Name the component of white light that has the longest wavelength.

5. Why do different components of white light deviate through different angles when passing though a prism?

6. 1s it necessary that the cross section of a prism be any particular type of triangle such as an equilateral triangle?

7. For which colour -violet or green-does glass have a larger refractive index?

8. What is scattering of light?

B. Short-Answer Questions

1. What is white light? Give a source of white light.

2. After white light passes through a glass prism, its components fall at different positions on a Screen. Why?

3. What do you understand by spectrum? How is a spectrum produced in the laboratory?

4. How can you recombine the components of white light after a prism has separated them?

5. What is the relation between the wavelength of light and the size of the particle causing scattering?

6. Why does the sky look blue on a clear, sunny day?

7. Smoke from a fire looks white. What can you deduce about the size of the particles of ash in it?

C. Long-Answer Questions

1. Describe an experiment to show that white light consists of lights of different colours.

2. Describe an experiment to show that certain particles Scatter more of some colours of light.

3. Explain why the colour of the sun looks different at times of the day.

D. Objective Questions

I. Pick the correct option.

1. When white light passes through a prism, it splits into its component colours. This phenomenon is called

(a) spectrum

(b) reflection

(c) refraction

(d) dispersion

2. The number of surfaces bounding a prism is

(a) 3

(b) 4

(C)5

(d) 6 

3. A deviation in the path of a ray of ight can be produced

(a) by a glass prism but not by a rectangular glass slab

(b) by a rectangular glass slab but not by a glass prism

(c) by a glass prism as well as a rectangular glass slab

(d) neither by a glass prism nor by a rectangular glass slab

4. The wavelengths corresponding to violet, yellow and red lights are λ_v, λ_y and λ_r, respectively.

(a) λ_v > λ_y > λ_r

(b) λ_v < λ_y < λ_r

(c)  λ_y < λ_v < λ_r

(d) λ_y < λ_r < λ_v

5. The sky looks blue on a clear, sunny day because or

(a) dispersion of light

(c) reflection of light

(b) scattering of light

(d) refraction of light

II. Fill in the blanks.

1. A sodium-vapor lamp emits .......... light.

2. By convention, the angle of incidence for the second refraction in a prism is denoted by .......

3. In a spectrum of white light, the two co appearing at the ends are....... and...........

4. The colour in the sequence VIBGYOR that least wavelength is..........

5. A small particle will scatter lights of ........... wavelength better.

Electricity

A. Very-Short-Answer Questions

1 Write the unit of electric potential,

2. Define the potential at a point.

3 Define the potential difference between two points.

4. A dry cell usually has a small cap at one end and a flat surface at the other end. Which of the two is at a higher potential?

5. Name the instruments used to measure electric current and potential difference respectively. Which of these is connected in series and which is of connected in parallel in a circuit?

6. What is the shape of the graph between V and i, where V is the potential difference between the ends of a wire and i is the current in it?

7. Consider the units volt, ohm and ampere. One of them is the same as the product of the other two. Which one is this?

8. Name three electrical appliances in which the heating effect of electric current is used.

9. Two bulbs have ratings 100 W, 220 V and 60 W,220 V. Which one has a greater resistance?

10. You have two resistors of resistances 30 Ω and 60 Ω. What resistances can you get by combining the two?

11. Draw a diagram to show two resistors R and R2 connected in series. (2006)

12. Two resistors of 5Ω and 10Ω are connected in series in a circuit. How does the current passing through them compare: (2006)

13. A wire of resistance 10 Ω is bent to form a closed Circle. What is the resistance across a diameter of the circle? (2005)

B. Short-Answer Questions

1. What is the difference between a conductor and an insulator? Give one example of each.

2. The current in a wire is one ampere. Explain this statement in terms of the charge flowing through the wire.

3. When do you say that the resistance of a wire is 1Ω?

4. Draw a circuit diagram for a circuit in which two resistors A and B are joined in series with a battery and a voltmeter is connected to measure the potential difference across the resistor A.

5. When are resistors said to be connected in series?

6. When are resistors said to be connected in parallel?

7.Why is tungsten suitable for making the filament of a bulb?

8. Why is tungsten not used as a fuse wire?

9. Alloys are preferred over metals for making the heating element of heaters. Why?

10. Silver is a better conductor of electricity than copper. Why then do we use copper wire for conducting electricity?

C. Long-Answer Questions

1. State Ohm's law. How can it be verified?

2. When the terminals of a cell are connected to the ends of an iron rod, electric current flows through the rod. When the terminals are Connected to the ends of a wooden rod, no current flows. Explain why, when the wooden rod also has a large number of electrons.

3. Define electric current and state its unit. How can Ohm's law be used to define ohm?

4. Deduce the expression for the equivalent resistance of the parallel combination of two

resistances R₁ and R₂.

5. Deduce the expression for the equivalent resistance of the two resistances R₁, and R₂, connected in series.

6. Derive an expression for the heat produced in time in a wire of resistance R, which is carrying a current i.

D. Numerical Problems

1. When a particle of charge 10 μC is brought from infinity to a point P, 2.0 mJ of work is done by the external forces. What is the potential at P?

2. Calculate the work done in taking a charge of 0.02 C from A to B if the potential at A is 20 V, and that at b is 30 V.

3. How much charge flows through a wire in 10 minutes if the current through it is 2.5 A?

4. A2-V cell is connected to a 1-Ω resistor. How many electrons come out of the negative terminal of the cell in 2 minutes?

5. The amount of charge passing through a cell in 4 seconds is 12 C. What is the current supplied by the cell?

6. A 6-V; battery is connected across a 5Ω resistor. Calculate the current passing through the resistor

7. When a 24-V battery is connected to a resistor, the current in it is 0.4 A. What is the resistance of the resistor? What would be the current through it when it is connected to a battery of 6 V?

8. In an experiment, the current flowing through a resistor and the potential difference across it are measured. The values are given below. Show that these values confirm Ohm's law, and find the resistance of the resistor.

i (ampere) 1.0  1.5  2.0  2.5   3.0

V (volt)     4.0  6.0  8.0  10.0  12

9. The resistivity of copper is 1.7 x10^-8 Ω m. (a) What length of copper wire of diameter 0.1 mm will have a resistance of 34 Ω? (b) Another copper wire of the same length but of half the diameter as the first is taken. What is the ratio of its resistance to that of the first wire?

10. Three resistors, each of resistance 12 Ω, are connected in parallel. What is the equivalent

resistance?

11. A uniform wire of resistance R is cut into two equal pieces, and these pieces are joined in parallel. What is the resistance of the combination?

12. You have three resisters of 9 ohms each. By combining them what can be (a) the highest

resistance, and (b) the lowest resistance? (c) How can you combine them to get a resistance of 12Ω?

13. How will you join the resistors of resistances 3Ω, 6Ω and 8Ω to get an equivalent resistance of 10Ω?

19. A 12-V battery connected to a bulb drives a current of 2.0 A through it. Find the energy supplied by the battery in 10 minutes.

20. A current of 1.5 A flows through a wire of 8 Ω. Find the amount of heat produced in 10 seconds.

21. A current of 2 A produces 200J of heat in a wire in a 81ven period of time. If the current is increased to 4A, how much heat will be produced in the sane time?

22. A bulb is rated 5.0 V, 100 mA. Calculate its rated power and resistance. (2006)

23. Calculate the resistance of a bulb rated 40 W, 230 V when in ON condition.

24 Calculate the current passing through a bulb rated 60 W, 240 V when it is connected to a 240-V power supply.

25. Two resistors of resistances 10Ω and 20Ω are joined in series. A potential difference of 12 V is applied across the combination. Find the power consumed by each resistor.

26. Two resistors of resistances 10Ω and 20Ω are joined in parallel. A potential difference of 12 V is applied across the combination. Find the power consumed by each resistor.

27. Calculate the energy consumed in kilowatt hours by a 60-W fan in 2 hours.

28. A heater draws 1100 W at 220 V. (a) Find the resistance of the heater when in ON condition (b)Calculate the kilowatt hours consumed in a week if the heater is used daily for four hours at the rated voltage.

29.A bulb used in a car is rated 12 V, 48 W. Find the energy consumed in one minute when the bulb is connected to (a) a 12-V battery, and (6) a 6-V battery.

E. Objective Questions

I. Pick the correct option.

1, The potential at a point is 20 V. The work done in bringing charge of 0.5 C from infinity to this point will be

(a) 20 J

(b) 10J

(c) 5J

(d) 40J

2. A negative charge released from a point A moves along the line AB. The potential at A is 15 V, and it varies uniformly along AB. The potential at B

(a) may be 10 V

(b) may be 15 V

(c) may be 20 V

(d) must be 15 V

3. A charge is taken from a point A to a point B. The work done per unit charge in the process is called

(a) the potential at A

(b) the potential at B

(c) the potential difference between B and A

(d) the current from A to B

4. Joule/coulomb is the same as

(a) watt

(b) volt

(c) ampere

(d) ohm

5. A voltmeter is used to measure

(b) electric current

(a) potential difference

(c) electric power

(d) resistance

6. On which of the following no 'plus' or 'minus' sign is marked?

(a) a cell

(b) an ammeter

(c) a voltmeter

(d) a resistor

7. An ammeter is always connected in ... and a voltmeter in .... The suitable words, in order, for

the blanks are

(a) series; series

(b) parallel; parallel

(c)parallel; series

(d) series; parallel

8. In a metal,

(a) all the electrons are free to move

(b) all the electrons are bound to their parent atoms

(c) there are no electrons

(d) some electrons are free to move

9. The free electrons of a metal are free to

(a) move on the surface only

(b) are free to escape through the surface

(c) are free to fall into the nuclei

(d) are free to move anywhere in the metal

10. The current in a wire depends

(a) only on the potential difference applied

(b) only on the resistance of the wire

(c) on both of them

(d) on none of them

11. Consider the following incomplete statement "Ohm's law relates potential difference with..... for a given resistance". The suitable choice for the missing word is

(a) power

(b) energy

(c) current

(d) time

12. Consider the following statements:

A: In series connection, the same current flows through each element.

B. In parallel connection, the same potential difference gets applied across each element.

(a) both A and B are correct

(b) A is correct but B is wrong

(c) A is wrong but B is correct

(d) both A and B are wrong

II. Mark the statements True (T) or False (F).

1. It is not possible to have a particle with charge 20 x10-19C.

2. An electron released from rest at a point A moves towards a nearby point B. The potential at A is higher than the potential at B.

3. A metal has a large number of electrons, but a nonmetal has only a small number of electrons.

4. The positive terminal of a cell is connected to the ernd A, and the negative terminal is connected to the end B of a metallic wire AB. Electrons flow in the wire in the direction B to A.

5. If two equal resistances are connected in parallel, the equivalent resistance is halved.

6. A thick wire has a larger resistance than a thin wire.

III. Fill in the blanks.

1. The resistance of a cylindrical piece of rubber is ........ than that of a similar piece of copper.

2. The kilowatt hour is the unit of .........

3. The equivalent resistance of two equal resistances connected in parallel is .. the value of each

resistance.

4. Three resistors are connected in series with a cell. If the current in each resistor is 2 A, that in the cell will be .........

5. Three resistors are connected in parallel with a battery. If the current in each resistor is 2 A, that in the battery will be .........

Magnetic effect of electric current

A. Very-Short-Answer Questions

1. How can you find the direction of a magnetic field at a point through which the magnetic line of force is given?

2. Sketch the shape of magnetic field lines near a straight wire carrying a current.

3. How will you show that the magnetic field produced by a current-carrying wire decreases with

distance from the wire? (2006)

4. How is the strength of the magnetic field at a point near a current-carrying wire related to the current? (2004)

5. A circular wire is carrying a current. Sketch the shape of the magnetic field lines in a plane that is perpendicular to the plane of the wire and passes through its center.

6. A circular loop carrying a current is placed on a horizontal surface. As seen from above, the current is in the clockwise direction. What is the direction of its magnetic field at the Centre? What is the direction of the magnetic field at a point outside the surface of the loop?

7. A vertical wire is carrying a current in the upward direction. It is placed in a magnetic field pointing towards the east. Find the direction of the force on the wire.

8. A beam of electrons can be thought of as an electric current whose direction is opposite the direction of the moving electrons. Suppose you find that an electron beam coming towards you horizontally through a magnetic field gets deflected towards your right. What is the direction of the magnetic field that bends the beam?  [Ans: Upwards]

9. A wire loop is moved into a magnetic field, You to find the direction of the current n a portion of the loop that is moving perpendicular to the field, Will you use Fleming's left-hand rule or right-hand rule?

10. An electric current is passed through a copper wire by connecting its ends to a battery. It is kept between the poles of a strong horseshoe magnet. There is a force on the wire due to the magnet. If you interchange the connections to the positive and negative terminals of the battery, and also the positions of the north and south poles of the magnet, what will be the change in the force on the wire due to the magnet?

11. What is the purpose of Fleming's right-hand rule?

12. A motor converts energy from one form to other. Name the two forms in sequence.

13. A generator converts energy from one form to other Name the two forms in sequence.

14. Which wire (live, neutral or earth) goes through a switch?

15. Are different electric appliances connected in sere or parallel in a house?

l6. What is the colour convention for live, neutral ad earth wires?

B. Short-Answer Type Questions

1.State Maxwell's right-hand thumb rule for finding the direction of the magnetic field due

current-carrying straight wire.

2. Why does a compass needle get deflected when a magnet is brought near it? Explain in tern

magnetic field.

3. Why cannot two magnetic field lines cut each other?

4. What is a solenoid? How is it different from a coil?

5. How is an electromagnet different from a permanent magnet?

6. Knowing the direction of the current, how will you determine the side on which the north pole is formed in an electromagnet?

7. Can a magnetic field be produced without using a magnet? If yes, how?

8. What is the use of the commutator in a DC motor?

9. State the principles (one sentence each) on which an electric motor and an electric generator are based.

10. What is the basic difference between an AC and a DC generator?

11. What is an overload in an electric circuit?

C. Long-Answer Questions

1. Describe an experiment to show that an electric current produces a magnetic field.

2. Describe an experiment to show that a magnetic field exerts a force on a current-carrying wire.

3. How will you show that the direction of the force exerted by a magnet on a current-carrying conductor depends on the directions of the magnetic field and the current?

4. You are given a strong bar magnet and a compass. Describe a method by which the magnetic field lines due to the bar magnet can be drawn.

5. What is an electromagnet? How can you make an electromagnet?

6. What is electromagnetic induction? Describe an experiment to demonstrate it. (2006)

7. What is induced current? Describe two was of producing an induced current in a coil.

8. State Fleming's left-hand rule. Draw a neat diagram showing the different parts of a DC motor. Explain its working.

9. What is Fleming's right-hand rule? With a neat diagram explain the working of an AC generator. (2005)

10. What do you understand by live, neutral and earth wires? Do all the three normally carry electricity?

11. What is the function of the earth wire in electric lines? Why is the metallic body of an electric

appliance connected to the earth wire?

12. What is a short circuit? How does a fuse help in case there is a short circuit?

13. An electric heater is rated 2 kW, 220 V. If a fuse is to be connected to it, should it be rated 5 A or 15 A?

D. Objective Questions

I. Pick the correct option.

1. A magnetic field line is used to find the direction of

(a) south-north

(b) a bar magnet

(c) a compass needle

(d) magnetic field

2. An electric current passes through a straight wire. Magnetic compasses are placed at the points A and B.

(a) Their needles will not deflect.

(b) Only one of the needles will deflect.

(c) Both the needles will deflect in the same direction.

(d) The needles will deflect in the opposite directions.

3. The magnetic field lines due to a straight wire carrying a current are

(a) straight

(b) circular

(C) parabolic

(d) elliptical

4. The magnetic field lines inside a long current carrying solenoid are nearly

(a) straight

(c) parabolic

(b) circular

(d) elliptical

5. The direction of the force on a current-carrying wire placed in a magnetic field depends on

(a) the direction of the current but not on the direction of the field

(b) the direction of the field but not on the direction of the current

(c) the direction of the current as well as the direction of the field

(d) neither the direction of the current nor the direction of the field

6. An electric current can be produced in a closed loop

(a) by connecting it to a battery, but not by moving a magnet near it

(b) by moving a magnet near the loop, but not by connecting a battery

(C) by connecting it to a battery, as well as by moving a magnet near it

(d) neither by connecting a battery nor by moving a magnet near it

7. Which of the following involves electromagnetic induction?

(a) A rod is charged with electricity.

(b) An electric current produces a magnetic field.

(c) A magnetic field exerts a force on a Current-carrying Wire.

(d) The relative motion between a magnet and a coil produces an electric current.

8. You have a coil and a bar magnet. You can produce an electric current by moving

(a) the magnet, but not the coil

(b) the coil, but not the magnet

(c) either the magnet or the coil

(d) neither the magnet nor the coil

9. An electric motor

(a) provides a constant potential difference

(b) measures electric current

(C) measures potential difference

(d) converts electrical energy into kinetic energy

10. A device that can be used to produce an electric current in a circuit is

(a) an ammeter

(b) a motor

(c) a generator

(d) a galvanometer

11. A commutator changes the direction of current in the coil of

(a) a DC motor

(b) a DC motor and an AC generator

(c) a DC motor and a DC generator

(d) an AC generator

12. An AC generator is connected to an electric appliance. In 10 revolutions of the armature, the

current in the appliance changes direction

(a) 5 times

(6) 10 times

(c) 20 times

(d) 40 times

13. Which of the following describes the common domestic power supplied in India?

(a) 220 V, 100 Hz

(b) 110 V, 100 Hz

(c) 220 V, 50 Hz

(d) 110 V, 50 Hz

14. In electric fittings in a house

(a) the live wire goes through the switch

(b) the neutral wire goes through the switch

(C)the earth wire goes through the switch

(d) no wire goes through the switch

15. An electric fuse is based on

(a) the heating effect of the current

(b) the chemical effect of the current

(c)the magnetic effect of the current

(d) none of these

16. An electric fuse can prevent accidents arising from

(a) an overload but not due to a short circuit

(b) a short circuit but not due to an overload

(c) an overload as well as a short circuit

(d) neither an overload nor a short circuit

I. Mark the statements True (T) or False (F).

1. Fleming's left-hand rule is used to find the direction of the magnetic field due to a straight current.

2. Maxwell's right-hand thumb rule is used to find the direction of the magnetic field due to a straight current.

3. The magnetic field at the center of a current-carrying coil is perpendicular to the plane of the coil.

4. The magnetic field lines inside a current-carrying solenoid are circular.

5. A motor is used to generate electricity from the mechanical motion of a coil.

6. A generator is used to generate electricity from the mechanical motion of a coil.

7. When a coil is moved towards a bar magnet placed perpendicular to it, an electric current is induced in the coil.

8. A battery provides an AC voltage.

9. If a coil and a magnet are moved in the same direction and with the same speed, an electric

current will be induced in the coil.

10. Two coils are kept near each other. If a constant current flows through one, a current will be induced in the other.

11. A fuse is connected in series with the circuit it protects.

12. The current through a short circuit is very high.

13. Fans, lamps, etc., are connected in parallel in household wiring.

14. The earth wire connected to an electric appliance does not carry an electric current unless a fault develops in the insulation of the wires.

III. Fill in the blanks.

1. The magnetic field lines near a current-carrying straight wire are ......... in shape.

2. In the statement of Fleming's left-hand rule, the forefinger represents the , the middle finger

represents the ........ and the thumb represents the........

3. A current passes through a wire from south to north. The direction of the magnetic field at a point vertically above the wire will be from ........ to.

4. A wire carries electric current from south to north. If it is placed in a magnetic field pointing towards the west, the force on it will be pointing towards the........

5. When a magnet is brought towards a metallic loop an electric current is produced in the loop. This is an example of electromagnetic ........

6. The.. Wire should first go to the switch and then to the appliance.......

7. The colours recommended for wires carrying have, neutral and earth lines are ....... and

respectively.

Source of energy

A. Very-Short-Answer Questions

1. Name two renewable and two nonrenewable sources of energy.

2. Name two conventional and two nonconventional sources of energy.

3 What is the ultimate source of the energy of fossil fuels?

4. Name four fuels that we get from fossil fuels.

5. Among fossil fuels, which is the least polluting?

6. What happens when coal burns incompletely?

7. What is a turbine?

8. What is hydroelectricity?

9. Mention two ways by which water can be used toproduce hydroelectricity. (2001)

10. What kind of energy does wind possess?

11. In the context of energy production, what is biomass?

12. What is the main constituent of biogas?

13. Which will cause the least amount of smoke when burnt-wood, cattle-dung cakes or biogas?

14. Why is solar energy considered renewable?

15. If 100 joules of solar energy is received by the upper atmosphere, how much of it reaches the

earth's surface?

16. What is a solar heating device?

17. In a box-type solar cooker what is the range of temperature that can be achieved in two to three hours?  (1995, '97)

18. Why is the inside surface of a box-type solar cooker blackened?

19. A solar cell transforms energy of one form into another form. What are these two forms of energy?

20. What is a solar panel? (1995)

21. Can a solar panel be used directly to power the TV set in your home?

22. What is geothermal energy? (1992)

23. What is nuclear fission?

24. What is a chain reaction?

25. What is nuclear fusion?

26. What is a nuclear reactor? (2006)

27. Name the process by which the sun produces its energy. (2006)

28. Which process is carried out at a higher temperature: nuclear fusion or nuclear fission? (1992, '94)

29. Give an example of how you can stop the wastage of energy.

B. Short-Answer Questions

1. Why are fossil fuels considered nonrenewable?

2. Can the excessive use of coal have a deteriorating effect on structures like the Taj Mahal? If yes, in what way?

3. How is charcoal produced?

4. Why is charcoal a better fuel than wood?

5. (a) Name the four gases Commonly present in biogas. (b) List two advantages of using biogas over fossil fuels. (2006)

6. When we harness wind energy, we harness solar energy indirectly. Explain. (2002)

7. How is electricity produced from wind energy? What are wind farms?

8. What are the advantages and limitations of wind energy?

9. Give two reasons why hydroelectricity is preferable to electricity froma coal-based plant. (2003)

10. Where are tidal power plants usually located? What are the limitations of tidal power?

11. Draw a diagram to show the basic design of a box-type solar cooker. (2000)

12. Explain the role of the glass top in a box type box type solar cooker.

13. What are the limitations of solar heating devices?

14. What are the advantages of solar energy?

15. Describe three uses of a solar panel.

16. What is the difficulty in the large-scale use of solar cells in electricity production?

17. How can electricity be generated from waves?

18. How are the wastes produced in nuclear power plants different from those produced at other power plants? What happens to the waste?

C. Long-Answer Question1s

1. What is the difference between renewable and nonrenewable sources of energy?

2. What are the characteristics of a good energy source?

3. What are the problems caused by burning fossil fuels?

4. Describe the construction and working of a biogas plant.

5. Why is hydro energy considered an indirect source of solar energy? Explain how hydro energy can be converted into electrical1 energy. State two advantages of hydro energy. (1996)

6. What causes wind to blow? Name a part of India where wind energy is commercially harnessed. Compare wind power and the power of flowing water for generating electricity. What are the hindrances in developing them? (2006)

7. Discuss the advantages and disadvantages of generating electricity from the wind.

8. Describe a box-type solar cooker, mentioning how the loss of heat is reduced in it.

9. Briefly discuss three principles based on which electricity can be generated from the ocean.

10. Describe how the difference in temperatures at different depths of the ocean can be utilized for generating electricity.

11. What are the problems created by the increased demand of energy? How can we solve them?

D. Objective Questions

I. Pick the correct option.

1. Which of the following is a renewable source o energy?

(a) Coal

(b) Natural gas

(c) Wood

(d) Petroleum

2. The purpose of the glass cover on top of a box-tyP solar cooker is too

(a) allow one to see the food being cooked

(b) allow more sunlight into the box

(c) prevent dust from entering the box

(d) reduce heat loss by radiation

3. A solar panel is made by combining a large number of

(a) solar cookers

(b) solar cells

(c) solar water heaters 

(d) solar concentrators

4. To work properly, wind-electric generators need wind speeds of at least about

(a) 1.5 km/h

(b) 15 km/h

(c) 150 km/h

(d) 1500 km/h

5. The site of a hydroelectric plant should be chosen carefully because it

(a) produces a large amount of carbon monoxide and carbon dioxide

(b) produces a large amount of electricity

(c) affects the organisms of the region

(d) is expensive

6. Electricity from the ocean can be generated based on utilizing

(a) kinetic energy of the waves but not stored thermal energy

(b) stored thermal energy but not kinetic energy of the waves

(c) kinetic energy of the waves as well as stored thermal energy

(d) neither kinetic energy of the waves nor stored thermal energy

7. Which energy is not derived from the sun?

(a) Nuclear energy

(b) Wind energy

(c) Biomass energy

(d) Ocean-wave energy

8. Which of the following is not biomass?

(a) Sun

(b) Rice husk

(c) Wood

(d) Cattle dung

9. The condition for producing biogas is

(a) air but not water

(b) water but not air

(c) air and water

(d) neither air nor water

10. Geothermal energy is feasible in regions that

(a) are near the sea

(b) have thermal plants

(c) have coal mines

(d) are over hot spots in the crust

II. Fill in the blanks.

1. A device transforming solar energy directly into electricity is called a .....

2. Wind is caused due to the..... heating of air near the earth's surface.

3. Hydro energy is..... reliable than wind energy.

4. The heat stored below the earth's surface is called ....... energy.

5. The main constituent of charcoal is ....

6. One important by-product of a biogas plant is .......

7. Solar cells are made from special materials called .......

8. A nuclear reaction in uranium starts when a slow-moving ... is absorbed by the nucleus of U-235.