Question

A current of 6 A flows through the heater when the electric heater is connected to 120 V supply.How much heat will it generate if the same heater is connected to 220 V supply for 10 second?

• A. 12.1 kJ
• B. 24.2 KJ
• C. 18.3 KJ
• D. 30.4 KJ

Answer 1

The correct option is B 24.2 KJ

$V_1=120V,I_1=6Aand{V}_2=220V$.
Let the resistance offered by the heater be R.
When first voltage supply is connected to the heater
We know, $V_1=I_{1}R$
$120=6\times R$
$R=20\Omega$
If we connect the same heater to the second supply voltage
Substituting values in equation, $V=IR$
$220=I\times 20$
$I=11A$
Heat Generated , $H=I^{2}RT$
$H={11}^2\times 20\times 10=24.2KJ$