Question

An electric heater is connected to $120\text{V}$ supply. A current of $6\text{A}$ flows through the heater. How much is the resistance across the heater? How much current would flow if the same heater is connected to $220\text{V}$ supply?

• A. $20\Omega ,11\text{A}$
• B. $20\Omega ,6\text{A}$
• C. $35\Omega ,11\text{A}$
• D. $35\Omega ,6\text{A}$

Answer 1

The correct option is A $20\Omega ,11\text{A}$

Given,
First supply voltage, ${\text{V}}_1=120\text{V}$,
Current flowing through the heater, $\text{I}=6\text{A}$
Second supply voltage, ${\text{V}}_2=120\text{V}$
Let, the resistance offered by the heater be $\text{R}$.
First voltage supply is connected to the heater.
We know,
$\text{V}=\text{IR}$
So, on substituting the values,
$120=6\times \text{R}$
$⟹\text{R}=20\Omega$
Therefore, the resistance offered by the heater is $20\Omega$.
Second voltage supply is connected to the heater:
On substituting values in equation, $\text{V}=\text{IR}$
$220=\text{I}\times 20$
$\text{I}=11\text{A}$
Therefore, the amount of current flowing is $11\text{A}$.