Chapter 16 - Electric Potential, Energy, and Capacitance - Learning Path Questions and Exercises - Exercises - Page 593: 41

2.2 V

Energy $E=Power\times time=0.50\,W\times5.0\,s=2.5\,J$ The expression connecting energy with the terminal voltage is $E=\frac{1}{2}CV^{2}$ $\implies V=\sqrt {\frac{2E}{C}}=\sqrt {\frac{2\times2.5\,J}{1.0\,F}}=2.2\,V$