Current Electricity
6.0 Heating effect of current
6.0 Heating effect of current
The phenomenon of production of heat in a resistor by the flow of an electric current through it is called the heating effect of current or joule heating.
In presence of electric field, electrons drift in a direction opposite to electric field. During this drifting motion, electrons collide with ion or atoms of metal.
In these collisions, electron loses energy which appears as heat energy.
The amount of energy dissipated as heat in conductor in time $t$ is, $$H = VIt = {I^2}Rt = \frac{{{V^2}t}}{R}\ Joules$$
According to this law, heat produced in resistor is,
1. directly proportional to the square of current for given $R$.
2. directly proportional to resistance $R$ for given $I$.
3. inversely proportional to the resistance $R$ for given $V$.
4. directly proportional to the time $t$ for which current flows through the resistor.
Electric power
Electric power is defined as the rate of electric energy supplied per unit time to maintain the flow of electric current through a conductor. $$P = VI = {I^2}R = \frac{{{V^2}}}{R}$$
SI unit of power is $Watt$, where $1W=1VA$
Electric energy
The total work done by the source in maintaining an electric current in a circuit for a given time $t$ is called electric energy consumed in the circuit. $$W = Pt = {I^2}Rt\ Joule$$
Commercial unit of energy is $1kWh$.
where,
$1kWh = 3.6 \times {10^6}joule$
Question 15. An electric current of $3.0A$ flows through a resistor of 16$\Omega $. What is the rate at which heat energy is produced in the resistor?
Solution.
Given $I = 3A$ , $R=16\Omega $
Powe is defined as the rate of production of heat energy. So, $$P = {I^2}R = {3^2} \times 16 = 144$$W
