Question

If current flowing in a conductor changes by 1% then power consumed will change by

• A. 10%
• B. 2%
• C. 1%
• D. 100%

Answer 1

Answer: (B)

2%

If initial current is $I$, after $1\%$ change the current becomes $I^{\prime }=I+I\left(1/100\right)=1.01I$
Initial power is: $P=I^{2}R$ and final power, $P^{\prime }=i^{\prime 2}R=(1.01I{)}^{2}R$
Thus, $\frac{P^{\prime }}{P}=\frac{(1.01{)}^2}{1}=1.02$
Thus, % of rise in power $=\frac{P^{\prime }-P}{P}\times 100=[\frac{P^{\prime }}{P}-1]\times 100=(1.02-1)100=2$ %