1. Define electric circuit.
The path through which current flows is called an electric
circuit.
2. Distinguish between closed circuit and open circuit.
Closed circuit (complete Open circuit (incomplete
circuit) circuit)
1. There is no break in 1.There is a break in
between the circuit between the circuit
2. Current flows in a 2.current does not flow in
closed circuit. an open circuit
3. Appliance will work in 3.Appliance will not work
a closed circuit . in an open circuit.
3.What is battery?
Combination of two or more cells is known as battery.
4. What is circuit diagram?
The schematic representation of an electric circuit using
the symbols of electric components is known as circuit
diagram.
5. What are the effects of electric current?
Heating effect, magnetic effect and chemical effect.
6. What do you mean by heating effect of electric current?
When electric current passes through certain wire ,heat energy is
produced. This effect of electric current is called heating effect of
electric current.
7. Name some devices which uses heating effect of electric
current?
Electric iron, electric heater, electric toaster etc.
8. What is heating element?
The coil of wire which gets heated up when electric current passes
through it is called heating element.
9. On what factors does the amount of heat produced in a wire
depends.
The amount of heat produced in a wire depends on its material,
length and thickness.
10. What is fuse?
Fuse is a safety device in an electric circuit which melts and
breaks the circuit when excessive current flows through it.
11. What are the characteristics of a fuse wire?
Fuse wire is made up of special material which has low
melting point and high resistance.
12. What is the working principle of a fuse ?
Fuse works on the basis of heating effect of electric current.
13. How does fuse protect the electric circuit?
In all buildings fuses are inserted in all electrical circuits.
There is a maximum limit on the current which can safely
flow through a circuit. If by accident the current exceeds this
safe limit, the wires may become overheated and may cause
fire. If a proper fuse is there in the circuit, it will blow off and
break the circuit. A fuse is thus a safety device which
prevents damages to electrical circuits and possible fires.
14. What are the two reasons for excessive current in an
electric circuit?
One reason for excessive currents in electrical circuits is the
direct touching of wires. This may happen if the insulation on
the wires has come off due to wear and tear. This may cause
a short circuit. Another reason for excessive current can be
the connection of many devices to a single socket. This may
cause overload in the circuit.
15. When does a short circuit occur?
When the insulation on the wires has come off due to wear
and tear, the wires may come in contact with each other.
This may lead to short circuit and the current rises rapidly
and hence electric fires can occur.
16. What is over loading?
When too much current flows through an electric circuit than
it can tolerate is called overloading.
17. What do you mean by magnetic effect of electric current?
When electric current passes through a wire, it behaves
like a magnet. This is called the magnetic effect of the
electric current..
18. What is electromagnet?
A current carrying coil of an insulated wire wrapped
around a piece of iron is called an electromagnet.
19. When the current is switched on through a wire, a
compass needle kept nearby gets deflected from its
north-south position. Explain.
When the current is switched on through a wire, the wire
starts behaving as a magnet. Hence, when a compass
needle is placed near the given current carrying wire, it
gets influenced by the magnetic effect of electric current
and gets deflected from its north- south position.
20. What are the ways of increasing the strength of
electromagnet?
(i) By increasing the strength of electric current.
(ii) By increasing the number of turns of the coil of wire.
21. What are the uses of electromagnet?
(i) The electromagnets are also used to separate magnetic
material from the junk.
(ii) Doctors use tiny electromagnets to take out small pieces of
magnetic material that have accidentally fallen in the eye.
(iii) Electromagnets are used in electric bell, electric motor etc .
22.What is the principle of electric bell?
Electric bell works on the basis of magnetic effect of electric current
23. Describe the structure and working of electric bell with a labelled
diagram.
Structure& working given in text book
