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1. a. State Joule’s law of heating.
Joule’s law of heating states that the heat produced in any resistor is
• Directly proportional to the passing through the resistor.
• Directly proportional to the of the resistor.
• Directly proportional to the for which the current is passing through the resistor.
b. An alloy of nickel and chromium is used as the heating element. Why?
In all the electrical appliances, a coil of wire called an is present. When these appliances are switched on, flows through the circuit. This makes the element in the appliances to give out .
, an alloy of nickel and chromium, is used as a heating element in the electrical appliances. It is preferred as a heating element because
• It has .
• It has a .
• It is not .
• It has a .
• It is not .
In appliances:
The heating coil of an electric heater is made of nichrome wire. A spiral coil of nichrome wire is put in a groove inside a or any insulator frame. An is used as it does not gets heated up. Due to the high resistance, the wire becomes red hot when current is passed through it. Thus, the heat produced by nichrome is utilised for .
c. How does a fuse wire protect electrical appliances?
An electric fuse is a safety device that to electrical appliances due to excessive current flow.
The fuse consists of a ceramic body and two points for connecting the fuse wire. The fuse wire is an alloy containing . Some properties of fuse wire are listed below.
• It has .
• It has a .
• It has a .
Due to high resistance, some materials in the wires quickly and break when a large amount of current is passed through them. Electric fuse wire connected in series in electrical circuits uses a material with a low melting point.
There is a safety limit for the current to flow in the circuit. The wire gets overheated and melts if the exceeds this limit due to Joule’s heating effect.
In this scenario, the fuse will blow off when the circuit is broken. The safety device, fuse prevents the circuits from any damages occurring due to fire.
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