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Class 7 Electricity and Its Effect

Total questions: 47

Worksheet time: 47mins

Name
Class
Date
1.

When an electric current flows through a copper wire AB as shown in Figure14.1, the wire

a)

deflects a magnetic needle placed near it

b)

becomes red hot

c)

gives electric shock

d)

behaves like a fuse

2.

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.

3.

Three bulbs A, B, C are connected in a circuit as shown in Figure 14.2. When the switch is ‘ON’

a)

bulb C will glow first

b)

bulb B and C will glow simultaneously and bulb A will glow after some time

c)

all the bulbs A,B and C will glow at the same time

d)

the bulbs will glow in the order A, B and C

4.

When a switch is in OFF position, 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

5.

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.

6.

Which property of a conducting wire is utilised in making electric fuse?

a)

High boiling point

b)

Low boiling point

c)

High melting point

d)

Low melting point

7.

Name the device used these days in place of electric fuses in electrical circuits.

a)

Miniature Circuit Breaker

b)
voltage regulator
c)
power strip
d)
fuse box
8.

Fill in the blanks: Our body is a ________________ of electricity.

a)
magnet
b)
conductor
c)
generator
d)
insulator
9.

Fill in the blanks: An electric cell produces electricity from the __________
___________ in it.

a)
metals
b)
water
c)
light
d)
chemicals
10.

Fill in the blanks: In an electric circuit a fuse is a ________________ to
prevent possible fire.

a)
fire extinguisher
b)
light bulb
c)
safety device
d)
screwdriver
11.

Fill in the blanks: A combination of two or more cells is called a _________.

a)

parallel

b)

battery

c)

series

d)

bulb

12.

Paheli does not have a night lamp in her room. She covered the bulb of her room with a towel in the night to get dim light.
Has she taken the right step? Give one reason to justify your answer.

a)

No, wastage of electricity

b)

No, use paper instead of cloth

c)

No, it might burn cloth

d)

No, use wet cloth

13.

Why are compact fluorescent lamps (CFLs) preferred over
electric bulbs?

a)
CFLs have a higher risk of causing fires
b)
CFLs are more energy-efficient, last longer, and produce less heat.
c)
CFLs are more expensive to purchase initially
d)
CFLs are less environmentally friendly
14.

Why is an electric fuse required in all electrical appliances?

a)
To protect the appliance and prevent damage in case of a power surge or short circuit.
b)
To improve the aesthetic appeal of the appliance
c)
To increase the energy consumption
d)
To make the appliance heavier
15.

Can we use the same fuse in a geyser and a television set?
Explain.

a)
Yes, the same fuse can be used in a geyser and a television set.
b)
No, fuses are not needed in either a geyser or a television set.
c)
It depends on the brand of the geyser and television set.
d)
No, we cannot use the same fuse in a geyser and a television set.
16.

Name two electric devices for each where (i) heating effect of current is used and (ii) magnetic effect of current is used.

a)

Electric kettle, Electric Bell

b)
Fan, Blender
c)
Refrigerator, Microwave
d)
Electric iron, Hairdryer
17.

Why do we cover plug pin holes which are within the reach of children with cellotape or a plastic cover when not in use?

a)
To enhance the aesthetic appeal of the plug
b)
To make it easier for children to play with
c)
To increase the risk of electric shocks
d)
To prevent accidental electric shocks or short circuits.
18.

Boojho made an electromagnet by winding 50 turns of wire over an iron screw. Paheli also made an electromagnet by winding 100 turns over a similar iron screw. Which electro magnet will attract more pins? Give reason

a)

Paheli's electromagnet with 100 turns, strong electromagnet

b)

Boojho's electromagnet with 50 turns, strong electromagnet

c)

Paheli's electromagnet with 100 turns, weak electromagnet

d)

Boojho's electromagnet with 50 turns, weak electromagnet

19.

Draw the symbols of the following circuit components: Electric Cell

a)

b)

c)

d)

20.

Draw the symbols of the following circuit components: Battery

a)

b)

c)

d)

21.

Draw the symbols of the following circuit components: switch in off position

a)

b)

c)

d)

22.

Draw the symbols of the following circuit components: Electric Bell

a)

b)

c)

d)

23.

How does the magnetic effect of electric current help in the working of an electric bell? Explain with the help of a diagram.

a)
The magnetic effect of electric current repels the iron armature away from the electromagnet, preventing the bell from ringing.
b)
The magnetic effect of electric current helps in attracting the iron armature towards the electromagnet, causing it to strike the bell and produce sound.
c)
The magnetic effect of electric current causes the bell to ring continuously without stopping.
d)
The magnetic effect of electric current attracts the iron armature towards the bell, bypassing the electromagnet.
24.

Electromagnet loses its magnetic property when

a)

(a) Current is very high

b)

(b) Current is switched OFF

c)

(c) Heat is increased

d)

(d) Current is switched ON

25.

A ___________ is used in torches.

a)

Generator

b)

Fuse

c)

Secondary Cell

d)

Dry Cell

26.

Electromagnet is used in _________

a)

Battery

b)

Dry Cell

c)

Electric Bell

d)

Fuse

27.

A device which prevents or allows the current to flow through it

a)

Motor

b)

Terminal

c)

Conductor

d)

Switch

28.

The metal which is poor conductor of electricity is _________

a)

Gold

b)

Iron

c)

Aluminium

d)

Mercury

29.

Electric Current is measured by a device called _______

a)

voltmeter

b)

ammeter

c)

electroscope

d)

none of these

30.

A device that break that electric circuit in case of excess current is called _______

a)

Switch

b)

Fuse wire

c)

Voltmeter

d)

Earth wire

31.

Study of relationship between electricity and magnetism is called _________

a)

current electricity

b)

electric magnetism

c)

magneto electricity

d)

electromagnetism

32.

Coils of heating devices are made up of ________

a)

Mercury

b)

Nichrome

c)

Copper

d)

Tungsten

33.

Electromagnet is based on

a)

Chemical effect of electric current

b)

Heating effect of electric current

c)

magnetic effect of electric current

d)

electro-chemical effect of electric current

34.

Filament of electric bulb is made up of _________

a)

nichrome

b)

tungsten

c)

silver

d)

copper

35.

Fuse wire is made up of alloys of

a)

High melting point

b)

low melting point

c)

low boiling point

d)

none of these

36.

Wire carrying current produce attracts the magnetic material due to

a)

magnetic field

b)

chemical effect

c)

heating effect

d)

all of these

37.

Fuse wire is used in electric circuit to prevent

a)

prevent the ammeter

b)

Us from electric shock

c)

Electrical appliances and circuit

d)

Prevent the insulator

38.

Why are symbols used for electronic components ?

a)

It makes it easier to draw the circuit diagrams

b)

it is essential to draw the circuit diagrams

c)

it helps to show the direction of flow of current in a circuit

d)

All of the above

39.

Heating effect of electric current is used in __________

a)

Electric watch

b)

Bread toaster

c)

Switch

d)

None of these

40.

In electrical wiring, the wire with black insulation is usually

a)

Fuse wire

b)

live wire

c)

earth wire

d)

neutral wire

41.

MCB in electric circuit stand for _______

a)

Miniature circuit breaker

b)

Maximum current breaker

c)

Minimum current breaker

d)

Molar current breaker

42.

When electric current flows through a conductor, the conductor becomes

a)

liquid

b)

vapour

c)

hot

d)

cold

43.

Electric current is said to pass through a wire when

a)

Only proton pass through it

b)

Only electron passes through it

c)

No particle pass through it

d)

Both electron and neutron pass through it

44.

Which of the following materials is a conductor?

a)

Silver

b)

Rubber

c)

Cloth

d)

Plastic

45.

A device that converts the electrical energy into heat energy is

a)

Motor

b)

Heater

c)

MP3

d)

Fan

46.

Nichrome is used a coil of heater because

a)

It has high resistance and high melting point

b)

Low resistance and high melting point

c)

High resistance and low melting point

d)

None of the above

47.

A fuse is fixed in a circuit in order to _________

a)

decrease the amount of current

b)

increase the amount of current

c)

increase the power consumed in the circuit

d)

safeguard against excessive current

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