Answer Happy

A parallel-plate capacitor is made of two square plates 30 cm on a side and 2 mm apart. The capacitor is connected to a 90-V battery. 1) What is the energy stored in the capacitor? (In p.) 2) With the battery still connected, the plates are pulled apart to a separation of 4 mm. What is the energy stored in the capacitor now? 1. J This time, starting from situation in (1), with the batteries disconnected (but capacitors still charged), the plates are pulled apart to a separation of 4 mm. What is the energy stored in the capacitor now? µJ Comparing your results in (2) and (3) above, it makes sense that the energy stored in the capacitor increases in (3), because the work done in separating the plates is stored as the electrostatic potential energy. In (2), why does the energy decrease even though work is done in separating the plates? The energy due to work done goes into the battery. The energy is not conserved in static electricity. A negative work is done in separating the plates. The energy stored in the capacitor does not include work done on the charges.