14 Electric Current and Its
Effects
MULTIPLE CHOICE QUESTIONS
1. When an electric current flows through a copper wire AB as
shown in Figure14.1, the wire
Fig. 14.1
(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.
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76 EXEMPLAR PROBLEMS
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 simulaneously 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.
A B C
Fig. 14.2
4. 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.
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ELECTRIC CURRENT AND ITS EFFECTS 77
(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.
VERY SHORT ANSWER QUESTIONS
6. Which property of a conducting wire is utilised in making
electric fuse?
7. Name the device used these days in place of electric fuses in
electrical circuits.
8. Fill in the blanks:
(i) Our body is a ________________ of electricity.
(ii) An electric cell produces electricity from the __________
___________ in it.
(iii) In an electric circuit a fuse is a _________ _______ to
prevent possible fire.
(iv) A combination of two or more cells is called a _________.
9. Unscramble the following words:
(i) TBTAYER
(ii) SFEU
(iii) HTRCO
(iv) HICWTS
10. 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.
11. Why are compact fluorescent lamps (CFLs) preferred over
electric bulbs?
12. Why is an electric fuse required in all electrical appliances?
SHORT ANSWER QUESTIONS
13. Can we use the same fuse in a geyser and a television set?
Explain.
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78 EXEMPLAR PROBLEMS
14. Name two electric devices for each where (i) heating effect of
current is used and (ii) magnetic effect of current is used.
15. Why do we cover plug pin holes which are within the reach of
children with cellotape or a plastic cover when not in use?
16. 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.
LONG ANSWER QUESTIONS
17. Your teacher has shown you the following activity.
Fig. 14.3
Activity: Teacher has wound a long insulated piece of wire
around an iron nail in the form of a coil. Free ends of the wire
are connected to a cell through a switch as shown in the Figure
14.3. The current is switched on and some pins are placed
near the ends of the nail.
Write down any three questions that come to your mind about
this activity.
18. Paheli took a wire of length 10 cm. Boojho took a wire of 5 cm
of the same material and thickness. Both of them connected
the wires as shown in the circuit given in Figure 14.4. The
current flowing in both the circuits is the same.
(i) Will the heat produced in both the cases be equal?
Explain.
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ELECTRIC CURRENT AND ITS EFFECTS 79
(ii) Will the heat produced be the same if the wires taken by
them are of equal lengths but of different thickness?
Explain.
Fig. 14.4
19. How does the magnetic effect of electric current help in the
working of an electric bell? Explain with the help of a diagram.
20. Draw the symbols of the following circuit components.
(i) electric cell
(ii) switch in off position
(iii) electric bulb
(iv) battery
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