Question

Two electric resistors have equal values of resistance $R$. Each can be operated with a power of $320watts\left(w\right)$ at $220volts$. If the two resistors are connected in series to a $110$ volts electric supply, then the power generated in each resistor is

• A. $90watts$
• B. $80watts$
• C. $60watts$
• D. $20watts$

Answer 1

The correct option is D $20watts$

Given - $V=220V,P=320W,V^{\prime }=110V$

Hence , resistance $R$ of each resistor $R=\frac{V^2}{P}=\frac{220\times 220}{320}\Omega$

As given resistors are in series ,therefore total resistance ,

$R^{\prime }=2R$

Hence , total power generated by both resistors at $110V$ ,

$P^{\prime }=\frac{V^{\prime 2}}{R^{\prime }}=\frac{110\times 110\times 320}{2\times 220\times 220}=40W$

Therefore power generated by each resistors ,

$P^{\prime \prime }=40/2=20W$