CBSE · Class 10 · Science · ElectricityWhat is Joule's heating effect of electric current? Derive the mathematical expression for it. Also, explain any two practical applications of heating effect of electric current in daily life.

Joule's Heating Effect of Electric Current\nWhen an electric current is passed through a high-resistance wire (like nichrome wire), the wire becomes very hot and produces heat. This phenomenon of production of heat in a resistor due to the flow of electric current through it is called Joule's heating effect of electric current.

Derivation of Formula\nLet a current $I$ flow through a resistor of resistance $R$ for a time $t$, under a potential difference $V$.

1. The amount of charge $Q$ flowing in time $t$ is given by: $$Q = I \times t$$
2. The work done ($W$) in moving this charge $Q$ across the potential difference $V$ is: $$W = V \times Q$$
3. Substituting $Q = I \times t$ into the work equation: $$W = V \times (I \times t)$$
4. According to Ohm's law, $V = IR$. Substituting this value of $V$: $$W = (IR) \times (I \times t)$$ $$W = I^2Rt$$ \nAssuming that all the electrical work done is converted into heat energy ($H$), we get: $$H = I^2Rt$$\nThis equation is known as Joule's law of heating.

Practical Applications

1. Electric Heating Appliances: Appliances such as electric irons, electric toasters, electric kettles, and water heaters work on Joule's heating effect. These devices use heating elements made of high-resistivity alloys like nichrome, which do not oxidize easily at high temperatures.
2. Electric Fuse: An electric fuse is a safety device used in domestic circuits to protect appliances from damage caused by overloading or short-circuiting. It consists of a thin wire made of a material with a low melting point (such as a copper-lead alloy). When excessive current flows, the fuse wire heats up, melts, and breaks the circuit, preventing further damage.