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Question
(a) How should the electric lamps in a building be connected so that switching on or off in a room has no effect on other lamps in the building? State one or more advantage of such an arrangement.
(b) Which effect of current is utilised in the working of an electric fuse? How does an electric fuse work?
(c) What is the usual colour of the insulation of (i) earth wire, and (ii) live wire?
(d) When does an electric short circuit occur? What harm can do it?
(e) Explain the purpose of earthing an electrical appliance.
(b) Which effect of current is utilised in the working of an electric fuse? How does an electric fuse work?
(c) What is the usual colour of the insulation of (i) earth wire, and (ii) live wire?
(d) When does an electric short circuit occur? What harm can do it?
(e) Explain the purpose of earthing an electrical appliance.
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Solution
(a) Electric lamps should be connected in parallel so that every lamp gets its separate current. In that condition, switching on and off in a room will not affect the other lamps in the building. Advantage of this type of connection is, if any appliances fail in the circuit or stop working, then it won't affect the other appliances, as in parallel connected every appliance get their separate current from the main circuit.
(b) Heating effect of current is utilized in the working of an electric fuse. A fuse is made such that it can allow only a particular amount of current to flow in the circuit. So, when a current more than the rating of the fuse starts flowing in the circuit, the wire of the fuse melts and it breaks the circuit. Therefore, no current flows further in the circuit, and no other appliances get any damage.
(c) (i)The usual colour of the earth wire is either green or yellow.
(ii) While the usual colour for the live wire is brown.
(d) An electric short-circuit occurs when the live wire comes in contact with the neutral in any circuit. A short-circuit can result in a flow of sudden high amount of current in the circuit, which may damage low rating appliances.
(e) The main purpose of earthing is to provide an immediate path to excess flow of current due to a fault in the circuit. This is done to prevent us from getting a shock. For this, the earthing wire is connected directly to the earth, so that whenever a high current flows in the circuit, it can be discharged directly to the ground.
(b) Heating effect of current is utilized in the working of an electric fuse. A fuse is made such that it can allow only a particular amount of current to flow in the circuit. So, when a current more than the rating of the fuse starts flowing in the circuit, the wire of the fuse melts and it breaks the circuit. Therefore, no current flows further in the circuit, and no other appliances get any damage.
(c) (i)The usual colour of the earth wire is either green or yellow.
(ii) While the usual colour for the live wire is brown.
(d) An electric short-circuit occurs when the live wire comes in contact with the neutral in any circuit. A short-circuit can result in a flow of sudden high amount of current in the circuit, which may damage low rating appliances.
(e) The main purpose of earthing is to provide an immediate path to excess flow of current due to a fault in the circuit. This is done to prevent us from getting a shock. For this, the earthing wire is connected directly to the earth, so that whenever a high current flows in the circuit, it can be discharged directly to the ground.
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