“The phenomena of production of heat energy in the conductor due to current flowing through it is called Heating Effect of Electric Current.”

Joule’s Law gives quantitative relation for heating effect of electric current . Consider a conductor having potential difference of V volts and resistance R Ω. Current flowing through the conductor can be calculated using Ohm’s Law as
I = V/R
∴ V = IR ……(1)
Let us consider that the current flows through the conductor for time t then total charge flowing through the conductor in time t is given as
Q = It ……(2)
The amount of work done W needed during the flow of charge Q through the conductor is given by Work done (W) = Potential Difference (V) Charge (Q)
i.e. W = V × Q ……(3)
∴ W = IR × It Joule
∴ W = I²Rt Joule
This work done get converted to heat energy
∴ H = I²Rt= VIt Joule
This relation is known as Joule’s Law

“Heat generated in a conductor is directly proportional to square of the current, resistance of conductor and time for which the current flows.”

∵ 4.18 Joule = 1 Calorie
∴ 1 Joule = 1/4.18 Calorie
∴ H=I²Rt / 4.18 Calorie

Different ways of representing the quantitative relations for Heating effect of electric current are as follows
or H = I²Rt= VIt = V²t/R Joule

1. Electric Bulb: Electric bulb consists of a filament. The filament is made of metal with very high melting point such as tungsten.When current passes through this filament, large amount of heat get generated. The filament becomes so hot that it starts emitting light. Normally bulbs are filled with nitrogen and argon gases to prevent the oxidation of the filament and hence to increase it’s life.
2. Electric Iron: Electric iron is used for ironing clothes. Electric iron consists of a coil of very high resistance covered with mica sheets. This arrangement is kept inside a heavy metal block. On passing electric current, the coil get heated. The coil is in contact with mica sheet. Mica sheet are good conductor of heat but bad conductor of electricity. Generated heat is transferred to mica sheet being in contact with the coil which in turn heat the metal in contact with it. This way heat is transferred to the metal body preventing current to enter in the metal body.



3. Electric Fuse: A very important application of heating effect of electric current is Electric Fuse. Under short circuit condition excess current flows through the circuit. The excess current causes damage to the device. To prevent this, electric fuse is kept in series with the device. Electric fuse is a piece of wire made from an alloy of low melting point but good conductivity such as alloy of lead and tin. If excess current flows through the circuit, due to heating effect of electric current there is rise in temperature of the fuse wire as a result the fuse wire melts and disconnects the device from the supply. In this way the device is protected from the damage. For the domestic purpose various fuse ratings available are 1A, 2A, 3A, 4A, 5A, 10A etc. A fuse is selected based on device current rating.





4. Industrial Use: Heating effect of electric current is useful in various industrial activities such as soldering, welding, cutting, drilling.
5. In Surgery: During a surgery, a fine heated platinum wire is used to cut the tissues much efficiently than the knife.

Numerical: Find the heat produced when a current of 0.5 A is passed through a coil of resistance 200Ω for 5 minutes.
Solution:
Given Data: Current I = 0.5 A,
Resistance R = 200Ω
time t = 5 minutes= 5×60 seconds = 300s
From Joule’s Law we have,
H =I²Rt / 4.18 Calorie
H =(0.5)² ×200×300 / 4.18 Cal.
H = 25× 200 ×300 /(100×4.18)Cal.
H = 3588.52 Cal.

This article is helpful for Class 10 Science

Keywords: Heating Effect of Electric Current, Applications of Heating Effect of Electric Current, Fuse, How fuse works, Joule’s Law, Electric Bulb, Electric Iron

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