Obtain an expression for the heat produced in a conductor when a voltage V is applied across it. Heating effect of electric current is desirable as well as undesirable. Explain this statement.

Explanation

Refer chapter for derivation.
Heating effect of electric current is used in many applications such as electric bulb, electric fuse, coils of heaters and boilers, etc. Hence, it is desirable. However, it undesirable in many cases because:
a] When electric current is passed through any device,, a part of it is used to heat the device. This leads to unnecessary loss of energy
b] In many devices overheating causes improper functioning and may sometimes damage the device.