Question

Heater coil is cut into 3 equal parts and only one part is now used in the heater instead of the original one.The heat generated by one part of the coil would be how much in comparison to that of the full length coil??

Answer 1

According to joule's law of heating, heat produced by the coil $=\frac{V^2}{R}t$........1
when it is cut into 3 equal parts, the resistance of each part is R/3
Thereby $H^{\prime }=\frac{V^2}{\frac{R}{3}}t$

or $H^{\prime }=\frac{3V^2}{R}t$................2

Now by comparing equations 1 and 2 we can write

$H^{\prime }=3H$

Thus the heat generated by one part of the coil is three times the heat generated by the full-length coil.