Effects of Electric Current - Heating Effect of Electric Current

The heating effect of electric current refers to the generation of heat when an electric current flows through a conductor. This effect is widely used in various devices and appliances, such as electric heaters, bulbs, and irons, to perform useful tasks.

How it Works:

When an electric current passes through a conductor (like a wire), the electrons collide with the atoms of the conductor. This collision causes the atoms to vibrate, which generates heat. The amount of heat produced depends on the current, the resistance of the conductor, and the duration of current flow.

Joule’s Law explains the relationship between the heat produced and the factors involved. The law states that the amount of heat produced (H) is directly proportional to

• The square of the current (I²)
• The resistance of the conductor (R)
• The time (t) the current flows.

Mathematically, this is expressed as : H = I²Rt

Where:

• H = Heat produced (in Joules)
• I = Electric current (in Amperes)
• R = Resistance of the conductor (in Ohms)
• t = Time (in seconds)

1. Electric Bulbs: In an electric bulb, a tungsten filament is used. When current flows through the filament, it gets heated to a high temperature (up to 3400°C), emitting both light and heat. The heating effect of the current in the filament is what makes the bulb glow.
2. Electric Heaters: Electric heaters make use of the heating effect by passing current through a resistive coil (usually made of Nichrome). This coil heats up and is used to heat water or air.
3. Electric Irons: The heating element in an electric iron is designed to get hot when the current passes through it. This heat is used to press clothes.
4. Toasters and Electric Cookers: Similar to electric heaters, these appliances use coils with high resistance. The current passing through these coils generates heat, which is used for cooking or heating food.

Uses of coil

The electric power is measured in watts (W), where 1 W is a small unit. In practice, we often use kilowatts (kW) to measure power.

• 1 kW = 1000 W
• If 1 kW of power is used for 1 hour, it will consume 1 kWh of energy, which is equal to:
  • 1 kWh = 1 kW × 1 hr = 1000 W × 3600 s = 3.6 × 10⁶ J (Joules)

The heating effect of electric current can be dangerous if the current exceeds safe limits. Overloading a circuit or a device can cause the wires or equipment to overheat, leading to fire hazards or damage to the electrical components.

• Short Circuits: A short circuit occurs when the live and neutral wires touch, causing a large current to flow, generating excessive heat. This can cause fires if inflammable materials are nearby.
• Fuse Wire: To prevent damage from excessive current, a fuse wire is used in electrical circuits. If the current exceeds the safe limit, the fuse wire melts and breaks the circuit, stopping the current flow and preventing further damage or fire.

• Miniature Circuit Breakers (MCBs): In modern electrical systems, MCBs are used instead of fuse wires. They automatically cut off the current if it exceeds the safe limit, providing better protection against overheating and overloading.

Overloading and Power Surges:

Overloading occurs when too many electrical devices are used at once, drawing excessive current from the transformer. If the transformer cannot handle the load, the fuse in the transformer melts, shutting down the supply to prevent damage.