Question

If the energy of a 100 $\mu$F capacitor charged to 6 kV could all be used to lift a 50 kg mass, what would be the greatest vertical height through which mass could be raised?

• A. 0.6 mm
• B. 3.6 m
• C. 1.2 mm
• D. 12 m

Answer 1

Answer: (B)

3.6 m

Answer 2

Energy stored in the capacitor is used in lifting the mass. \therefore \hspace25mm mgh = \frac{1}{2}CV^2 $\, \, 50 \times 9.8 \times h = \frac{1}{2} \times 100 \times 10^{-6} \times (6 \times 10^2)^2$ $\, \, 50 \times 9.8 \times h = \frac{1}{2} \times 100 \times 10^{-6} \times 36 \times 10^6$ \therefore \hspace20mm h = \frac{1800}{50 \times 9.8} = 3.6 \, m