An ideal parallel-plate capacitor consists of a set of two parallel plates of area separated by a very small distance 푑. this capacitor is connected to a battery that charges the capacitor such that the energy stored in the capacitor is 푈'. now the battery is disconnected and the separation between the plates is doubled, how much energy is stored in the capacitor?

The heater element of a 120 v toaster is a 5.4 m length of nichrome wire, whose diameter is 0.48 mm. the resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 ω·m. the toaster is operated at a voltage of 120 v. (a) what is the power drawn by the toaster? (b) if the cost of electricity is 12 ¢ per kilowatt-hour, and it takes 2 minutes to toast bread, how much does it cost for toasted bread? (c) when the heater element is at room temperature, is the resistivity in the nichrome wire greater than, less than, or equal to it’s resistivity when at operating temperature? explain.