Question

Why are alloys commonly used in electrical heating devices? Give reason.

Answer 1

Hint: Heat produced is directly proportional to the resistance of the circuit. Therefore, the substance used in the electrical heating device must have a very high resistance and melting point. With this you may understand why alloys are used in the heating devices.

Complete step by step answer:
Electrical heating devices work on the principle of Joule’s law of heating. When a current (i) passes through a body (conductor), the body heats up. The heat produced in the conductor depends on the current passing through it such that the heat produced is directly proportional to the square of the current.
This means that if we increase the value of current in the conductor, more heat will be produced in a given amount of time.
The heat produced by the conductor also depends on the resistance (R) of the conductor. The heat produced is directly proportional to the resistance of the conductor. More the resistance of the conductor, more is the heat produced in the conductor in the given amount of time.
The resistance of a conductor is directly proportional to the resistivity of the material of the conductor.
The reason why alloys are commonly used in the heating devices is that alloys are good conductors of heat. In addition, they have very high resistivity, which implies that the resistance of alloys is very large. Hence, the heat generated by the devices will be large.
The substance used in the heating device must have a high melting point so that it does not melt easily due to the heat produced. Alloys have a high melting point. This is one more reason why alloys are preferred in the heating devices.

Note: Note that by making the resistance in the circuit a very large value, the current in the circuit will be reduced.
According to Ohm’s law, V = iR ,
V is the potential difference across the resistance.
Therefore, $i=\dfrac{V}{R}$.
This means that for constant voltage current is inversely proportional to the resistance of the circuit. Hence, on increasing the resistance, the current will become less.