Heating Effect of Current Explained

The heating effect of current, also known as Joule heating, occurs when electrical energy is converted into heat energy as electric current flows through a resistive material. The amount of heat generated is given by the formula $H = I^2Rt$, where $I$ is the current, $R$ is the resistance, and $t$ is the time.

Analyzing Electrical Devices

We need to identify which device listed operates on a principle other than the heating effect of current:

• Bulb: An incandescent bulb uses a filament with high resistance. When current passes through it, the filament heats up intensely, producing light and heat. This is an example of the heating effect.
• Working of a fan: A fan utilizes an electric motor. Electric motors work on the principle of the motor effect, where the interaction between a magnetic field and an electric current produces mechanical force, causing rotation. While resistance in the motor windings generates some heat, the primary function is mechanical work, not heating.
• Electric iron: An electric iron contains a resistive heating element. When current flows, the element heats up significantly, transferring heat to the soleplate for ironing clothes. This is a direct application of the heating effect.
• Electric kettle: Similar to the iron, an electric kettle uses a resistive heating element (coil) to heat water. The heat generated by the current passing through the element is used to boil the water. This relies on the heating effect.

Conclusion on Fan Operation

The primary principle behind a fan's operation is the conversion of electrical energy into mechanical energy (rotation) via the motor effect. The other listed devices (bulb, electric iron, electric kettle) primarily function by harnessing the heat generated due to the electrical resistance, which is the heating effect of current.