Question

Nichrome and copper wires of the same length and same radius are connected in series. The same current is passed through them. Why does the nichrome wire get heated first?

Answer 1

1. When current flows through a wire, a part of electrical energy is used in doing work and the rest of the electrical energy gets converted into heat that results in the heating of the wire. This is known as the heating effect of current.
2. According to Joule's law of heating, the amount of heat produced$\left(H\right)$ in a wire is given by
3. $H=I^{2}Rt$ where $I$ is the current flowing through the wire, $R$ is the resistance of the wire and $t$ is the time for which current flows in the wire.
4. Since the same amount of current flows in both of the wires, the amount of heat generated depends on the resistance of the wire.
5. The larger is the resistance of the wire, the greater is the amount of heat generated.
6. Nichrome being an alloy has more resistance as compared to copper which is metal( as the resistivity of the alloy is more than metal). That is why nichrome wire gets heated first.