Heating Effect of Electrical Current

 Heating Effect of Electrical Current

The current is defined as the flow of electrons under the influence of the voltage or potential difference applied and maintained by a battery. The electrons repelled by the negative terminal and attracted by the positive terminal of the battery and it moves through the conductor and collides with other atoms of the material of the conductor. The conductor thus offers resistance to the flow of current. The electrical energy supplied by the battery is converted to heat energy in overcoming the resistance of the conductor. This is termed as heating effect of current.

Joule’s law of heating:

This effect is described by Joule's Law, which states that the heat (H) produced by a current (I) passing through a resistor (R) for a time (t) is given by:

H = I² x R x t2

Where:

H is the heat produced (measured in joules),

I is the current flowing through the conductor (measured in amperes),

R is the resistance of the conductor (measured in ohms),

t is the time for which the current flows (measured in seconds).

Joule’s Law of Heating states that heat produced in a circuit is directly proportional to the square of current flowing, resistance for current and time for which current flows.

• The heating effect is utilized in various electrical devices like electric heaters, toasters, and incandescent light bulbs, where electrical energy is intentionally converted into heat for use.
• However, in some application, it's important to minimize the loss of electrical energy in the form of heat (such as in electrical transmission lines) to prevent energy loss due to heat dissipation.
• It causes wear and tear of components.

Q. Why is the tungsten used almost exclusively for filament of electric lamps?

Tungsten wire inside the bulb becomes hot and emits light when current passes through it. Since it has a high melting point of 3380°C, it does not break. Also, due to the presence of gases like chemically inactive nitrogen and argon inside the bulb, the filament remains thermally isolated and its life increases.

Q. What is fuse? How it works?

A fuse is a safety device used in electrical circuits to protect against excessive current. It is a thin wire or strip made of a material that melts easily when subjected to high current, breaking the circuit and preventing damage or fire. It saves the electrical circuits and appliances from short-circuit and overloading.

Fuses are commonly used in electrical systems of homes, automobiles, appliances, and various electrical devices to prevent damage caused by short circuits or excessive current flow.

Solved Numerical:

100 J of heat are produced each second in a 4 Ω resistance. Find the potential difference across the resistor.

Given:

H = 100 J, R = 4 Ω, t = 1 s,

To find V =?

We know,

H = I² x R x t

To get current through the resistor

I = √ (H/R t)

  = √ [100 J/ (4 Ω × 1 s)]

  = 5 A

Thus the potential difference across the resistor, V

From Ohm’s Law’s

V = IR

   = 5 A × 4 Ω

   = 20 V.