Question

If a resistance coil is made by joining in parallel two resistor each of $20\Omega$. An EMF of $2\text{V}$ is applied across this coil for $100$ seconds. The heat produced in the coil is -

• A. $20\text{J}$
• B. $10\text{J}$
• C. $40\text{J}$
• D. $80\text{J}$

Answer 1

The correct option is C $40\text{J}$

The equivalent circuit can be drawn as -

The equivalent resistance of the circuit is,

$\text{R}=\frac{20\times 20}{20+20}=10\Omega$

So,

$P=\frac{V^2}{R}=\frac{2^2}{10}=0.4\text{W}$

Now, heat produced,

$H=Pt$

$\Rightarrow H=0.4\times 100=40\text{J}$

Hence, option $\left(C\right)$ is the correct answer.