SOLUTIONS OF WORKSHEET FOR OPEN BOOK TEST, CH 15(LIGHT), CLASS 7

Multiple Choice Questions:

1. (a) always a straight line

2. (a) Plane mirror

3. (a) virtual and erect

4. (c) plane mirror and convex mirror

5. (a) Concave mirror only

6. (b) 1 m

7. (b) concave mirror or convex lens

8. (b) only a concave mirror

9. (c) both convex mirror and convex lens

10. (b) concave lens provided the image is smaller than object.

Match the following:

Column A	Column B
(i) Concave lens	(g) Thinner in the middle
(ii) Always virtual image	(h) Concave lens
(iii) Changing position of image	(a) Lateral inversion
(iv) Wax paper	(f) Translucent
(v) Image obtained on screen	(e) Real image
(vi) Convex mirror	(b) Reflecting surface is bulged out
(vii) Used by dentists	(c) Concave mirror
(viii) White light composed	(d) Seven colours

Fill in the blanks:

1.  irregular

2. normal,plane

3. reflection

4. lateral inversion

5. concave

6. plane

7. convex

8. concave

Choose the true and false statements from the following:

1. True

2. True

3. True

4. False

5. False

6. False

7. True

WORKSHEET FOR OPEN BOOK TEST, CH 15(LIGHT), CLASS 7

 Question 1.

The path of the light is

(a) always a straight line
(b) a curved line
(c) a zig-zag line
(d) depends on the medium

Question 2.
Which one shows lateral inversion?
(a) Plane mirror
(b) Convex mirror
(c) Concave mirror
(d) All of these

Question 3.
Image formed by a plane mirror is
(a) virtual and erect
(b) real and erect
(c) virtual and inverted
(d) real and inverted

Question 4.
Boojho and Paheli were given one mirror each by their teacher. Boojho found his image to be erect and of the same size whereas Paheli found her image erect and smaller in size. This means that the mirrors of Boojho and Paheli are, respectively
(a) plane mirror and concave mirror
(b) concave mirror and convex mirror
(c) plane mirror and convex mirror
(d) convex mirror and plane mirror

Question 5.
Which of the following can be used to form a real image?
(a) Concave mirror only
(b) Plane mirror only
(c) Convex mirror only
(d) Both concave and convex mirrors

Question 6.
If an object is placed at a distance of 0.5 m in front of a plane mirror, the distance between the object and the image formed by the mirror will be
(a) 2 m
(b) 1 m
(c) 0.5 m
(d) 0.25 m

Question 7.
You are provided with a concave mirror, a convex mirror, a concave lens and a convex lens. To obtain an enlarged image of an object you can use either
(a) concave mirror or convex mirror
(b) concave mirror or convex lens
(c) concave mirror or concave lens
(d) concave lens or convex lens

Question 8.
An erect and enlarged image can be formed by
(a) only a convex mirror
(b) only a concave mirror
(c) only a plane mirror
(d) both convex and concave mirror

Question 9.
You are provided with a convex mirror, a concave mirror, a convex lens and a concave lens. You can get an inverted image from
(a) both concave lens and convex lens
(b) both concave mirror and convex mirror
(c) both convex mirror and convex lens
(d) both convex mirror and concave lens

Question 10.
An image formed by a lens is erect. Such an image could be formed by a
(a) convex lens provided the image is smaller than object.
(b) concave lens provided the image is smaller than object.
(c) concave lens provided the image is larger than object.
(d) concave lens provided the image is of the same size.

Match the following:

Column A	Column B
(i) Concave lens	(a) Lateral inversion
(ii) Always virtual image	(b) Reflecting surface is bulged out
(iii) Changing position of image	(c) Concave mirror
(iv) Wax paper	(d) Seven colours
(v) Image obtained on screen	(e) Real image
(vi) Convex mirror	(f) Translucent
(vii) Used by dentists	(g) Thinner in the middle
(viii) White light composed	(h) Concave lens

Fill in the blanks:

1. Uneven surfaces show ………………….. reflection.

2. Incident ray, the reflected ray ………………….. and lie in the same …………………..

3. Laws of ………………….. is applicable in playing back shots in the carroms.

4. Changing of right side to left is called …………………..

5. The inner surface of a steel spoon acts as a ………………….. mirror.

6. The outer surface of a flat steel plate acts as a ………………….. mirror.

7. The outer shining surface of a round bottom steel bowl acts as a ………………….. mirror.

8. The inner surface of the reflector of a torch acts as a ………………….. mirror.

Choose the true and false statements from the following:

1. Concave mirror is converging in nature.

2. Convex mirror is diverging in nature.

3. Plane mirror forms virtual image.

4. Concave mirror has a virtual focus.

5. Spherical mirrors do not obey laws of reflection.

6. During lateral inversion, the image becomes inverted.

7. Angle between incident ray and reflected ray is double that of the angle of incidence.

Solutions Of Chapter 15 LIGHT, Class 7 Science

 Q.1.Fill in the blanks:

(a) An image that cannot be obtained on a screen is called ___________ .
(b) Image formed by a convex is __________ always virtual and smaller in size.
(c) An image formed by a __________ mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a __________ image.
(e) An image formed by a concave __________ cannot be obtained on a screen.
Ans.(a) virtual image (b) mirror (c) plane (d) real (e) lens

Q.2.Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)
(b) A concave lens always form a virtual image. (T/F)
(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F)
(d) A real image cannot be obtained on a screen. (T/F)
(e) A concave mirror always form a real image. (T/F)
Ans. a) F (b) T (c) T (d) F (e) F

Q.3. Match the items given in Column I with one or more items of Column II

Q.2.Mark ‘T’ if the statement is true and ‘F’ if it is false:Q.1.Fill in the blanks:
(a) An image that cannot be obtained on a screen is called ___________ .
(b) Image formed by a convex is __________ always virtual and smaller in size.
(c) An image formed by a __________ mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a __________ image.
(e) An image formed by a concave __________ cannot be obtained on a screen.
Ans.(a) virtual image (b) mirror (c) plane (d) real (e) lens

(a) We can obtain an enlarged and erect image by a convex mirror. (T/F)
(b) A concave lens always form a virtual image. (T/F)
(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F)
(d) A real image cannot be obtained on a screen. (T/F)
(e) A concave mirror always form a real image. (T/F)
Ans. a) F (b) T (c) T (d) F (e) F

Q.3. Match the items given in Column I with one or more items of Column II

Ans.
Q.4.State the characteristics of the image formed by a plane mirror.

Ans.(i) Plane mirror forms an erect image.
(ii) It forms a virtual image.
(iii) Size of the image is same as that of the object.
(iv)Image is formed at the same distance behind the mirror as the object stands in front of it.
(v) Image formed is a laterally inverted image i.e., right hand side of the object seems to be the left hand side and vice-versa.

Q.5.Find out the letters of English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.
Ans.Letters like A, H, I, M, O, T, U ,V, W etc. appear same when seen through a plane mirror

Q.6.What is a virtual image? Give one situation where a virtual image is formed.
Ans.The image which cannot be taken on a screen is called virtual image. When some object is placed very close to the concave mirror we don’t get any image on the white screen placed behind the mirror. Such image is called virtual image.

Q.7. State two differences between a convex and a concave lens.

Q.8. Give one use each of a concave and a convex mirror.

Ans. Use of concave mirror:
Concave mirror is used by dentists to examine the teeth.
Use of convex mirror:
Convex mirror is used as side view mirror in vehicles

Q.9. Which type of mirror can form a real image?
Ans. Concave mirror can form a real image.

Q.10. Which type of lens forms always a virtual image?
Ans. Concave lens always forms a virtual image.

Choose the correct option in Questions 11-13:

Q.11. A virtual image larger than the object can be produced by a
(i) concave lens (ii) concave mirror (iii) convex mirror (iv) plane mirror

Ans. (ii) concave mirror

Q.12. David is observing his image in a plane mirror. Die distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be
(i) 3 m (ii) 5 m (iii) 6 m (iv) 8 m

Ans. (iii) 6 m

Q.13. The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear mew mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be
(i) 1 m/s (ii) 2 m/s (iii) 4 m/s {iv) 8 m/s

Ans. (ii) 4 m/s

REVISION TEST, CH 13 and 14, Class 7

 1. Our body is a ………………….. of electricity.

2. An electric cell produces electricity from the ………………….. in it.

3. In an electric circuit a fuse is a ………………….. to prevent possible fire.

4. A combination of two or more cells is called a ………………….. .

5. The coil of wire in an electric heater is called an ………………….. .

6. The wire gets ………………….. when an electric current passes through it.

7. We must look for ………………….. mark on electrical appliances.

8. When electric current passes through a wire, it behaves like a magnet. It is the ………………….. effect of current.

9. Crane has a strong ………………….. attached to it.

10. In a simple pendulum, the metallic ball suspended by thread is called its …………………

11. The distance covered by an object in a ………………… is called its speed.

12. Time period of a pendulum depends on its …………………

13. Motion of objects can be presented in pictorial form by their ………………… graph.

14. The distance-time graph for the motion of an object moving with a constant speed is a …………………

15. A simple pendulum takes 84 sec. to complete 40 oscillations. What is its time period?

Electric Current and Its Effects Class 7 Solutions of WORKSHEET

1: (a) positive terminal of one cell is connected to the negative terminal of the next cell

2: (c) Can be placed anywhere in the circuit

3: (d) All of these

4: (b) element

5: (d) all of these

6: (b) ISI

7: (a) deflects a magnetic needle placed near it

8: (c) There is a minimum limit on the current which can safely flow in the electric circuits.

9: (b) (ii) and (iii) are correct

10: (d) We should never turn the switch in ON position.

Match the following:

Column A	Column B
(i) Switch	(f) Turns the circuit ON and OFF
(ii) Battery	(e) Supplies current to the circuit
(iii) Element	(a) Coil of wire which heats up when electricity current is supplied
(iv) Filament	(h) Wire in the bulb which glows
(v) Fuse	(b) Blows off, if the current exceeds safe limit
(vi) MCBs	(g) Turn OFF if current exceeds safe limit
(vii) CFL	(c) Consumes less energy than a bulb
(viii) ISI	(d) Mark that ensures that the electric appliance is safe to handle

Electric Current and Its Effects Class 7 WORKSHEET

 Question 1.

In making a battery
(a) positive terminal of one cell is connected to the negative terminal of the next cell
(b) positive terminal of one cell is connected to the positive terminal of the next cell
(c) negative terminal of one cell is connected to the negative terminal of the next cell
(d) none of the above

Question 2.
Where can the key or switch be placed in the circuit?
(a) Left side of the battery
(b) Right side of the battery
(c) Can be placed anywhere in the circuit
(d) Near the positive terminal of the bulb

Question 3.
Which one of the following is based on the heating effect of current?
(a) Geyser
(b) Hair dryer
(c) Immersion rod
(d) All of these

Question 4.
The coil of wire contained in an electric heater is known as
(a) component
(b) element
(c) circuit
(d) spring

Question 5.
The amount of heat produced in a wire depends on
(a) material
(b) length
(c) thickness
(d) all of these

Question 6.

Which mark is necessary on electric appliances?
(a) AGMARK
(b) ISI
(c) FICCI
(d) KSK

Question 7.
When an electric current flows through a copper wire AB as shown in Figure, the wire

(a) deflects a magnetic needle placed near it
(b) becomes red hot
(c) gives electric shock
(d) behaves like a fuse

Question 8.
Choose the statement which is not correct in the case of an electric fuse.
(a) Fuses are inserted in electric circuits of all buildings.
(b) There is a maximum limit on the current which can safely flow through the electric circuits.
(c) There is a minimum limit on the current which can safely flow in the electric circuits.
(d) If a proper fuse is inserted in a circuit it will blow off if current exceeds the safe limit.

Question 9.
When a switch is in OFF position.
(i) circuit starting from the positive terminal of the cell stops at the switch.
(ii) circuit is open.
(iii) no current flows through it.
(iv) current flows after some time.
Choose the combination of correct answer from the following:
(a) all are correct
(b) (ii) and (iii) are correct
(c) only (iv) is correct
(d) only (i) and (ii) are correct

Question 10.
Which of the following precautions need not be taken while using electric gadgets / appliances/circuit?
(a) We should never touch a lighted electric bulb connected to the mains.
(b) We should never experiment with the electric supply from the mains or a generator or an inverter.
(c) We should never use just any wire or strip of metal in place of a fuse.
(d) We should never turn the switch in ON position.

Match the following:

Column A	Column B
(i) Switch	(a) Coil of wire which heats up when electricity current is supplied
(ii) Battery	(b) Blows off, if the current exceeds safe limit
(iii) Element	(c) Consumes less energy than a bulb
(iv) Filament	(d) Mark that ensures that the electric appliance is safe to handle
(v) Fuse	(e) Supplies current to the circuit
(vi) MCBs	(f) Turns the circuit ON and OFF
(vii) CFL	(g) Turn OFF if current exceeds safe limit
(viii) ISI	(h) Wire in the bulb which glows

Electric Current and its effects, Chapter 14 Class 7 Science

 Q.1.Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position and battery.

Ans.

Q.2.Draw the circuit diagram to represent the circuit shown in fig. 14.9.

Q.3.Fig. 14.11 shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.

Ans.

Q.4.The bulb in the circuit shown in fig. 14.13 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

Ans.Problem in this circuit is the combination of two cells. In the circuit positive terminal of one cell should be connected with negative terminal of other to make the bulb glow

5. Name any two effects of electric current.

Solution:

i) Heating effect of electric current

ii) Magnetic effect of electric current

6. When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.

Solution:

When the current is switched on through a wire, magnetic field is created around it hence we see deflection in the compass needle kept nearby.

7. Will the compass needle show deflection when the switch in the circuit shown by Fig.14.24 is closed?

Solution:

No , compass needle does not show deflection when the circuit is a closed, magnetic field is not created until current is flowing through the circuit.

8. Fill in the blanks:

(a) Longer line in the symbol for a cell represents its terminal.

(b) The combination of two or more cells is called a .

(c) When current is switched ‘on’ in a room heater, it .

(d) The safety device based on the heating effect of electric current is called a .

Solution:

(a) Longer line in the symbol for a cell represents its positive terminal.

(b) The combination of two or more cells is called a battery.

(c) When current is switched ‘on’ in a room heater, it produces heat .

(d) The safety device based on the heating effect of electric current is called a fuse .

9. Mark ‘T’ if the statement is true and ‘F’ if it is false:

(a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (T/F)

(b) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)

(c) An electromagnet does not attract a piece of iron. (T/F)

(d) An electric bell has an electromagnet. (T/F)

Solution:

a) False

b) True

c) False

d) True

10. Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.

Solution:

No, because plastic does not have magnetic property to get attracted to a magnet hence magnet cannot be used to separate plastic bags.

11. An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response.

Solution:

It is not a wise idea to replace fuse by a piece of wire, as it has very low melting point. In case of metal piece, melting point will be high and the circuit will be intact in case there is overload or overheat.

12. Zubeda made an electric circuit using a cell holder shown in Fig. 14.4, a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.Solution:

Reasons maybe two

i) The connecting wire may be loose

ii) The electric cell may be used up

iii) switch may not be functioning well

iv) cell power has been exhausted

13. In the circuit shown in Fig. 14.25

(i) Would any of the bulb glow when the switch is in the ‘OFF’ position?

(ii) What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?

Solution:

i) No, the bulb will not glow as the circuit is not complete when the switch is off

ii) If the switch is On positions, all the bulbs glow simultaneously.