Question

The internal resistance of a primary cell is 4 $\Omega$. It generates a current of 0.2 A in an external resistance of 21$\Omega$. The rate of chemical energy consumed in providing the current is

• A. $0.42J{s}^{-}1$
• B. $0.84J{s}^{-}1$
• C. $1J{s}^{-}1$
• D. $5J{s}^{-}1$

Answer 1

The correct option is C $1J{s}^{-}1$

By conservation of energy.
Chemical energy consumed per sec $=$heat energy produced per sec$=I^2(R+r)=\left(0.2{)}^2\right(21+4)=1J{s}^{-1}$