Which device uses a small separation between conductors to store electrical energy?

Which device uses a small separation between conductors to store electrical energy?

• A. Resistor
• B. Inductor
• C. Transistor
• D. Capacitor

Answer: (D)

The key idea is energy storage in an electric field between two conductors separated by a dielectric. A capacitor does this by having two conductors close together with an insulating material between them. When you apply a voltage, charges accumulate on the plates, creating an electric field in the space between them. The energy is stored in that field, not in the conductors themselves. The amount of energy depends on the capacitance and the voltage, given by U = 1/2 C V^2. Capacitance increases when the separation between the plates is smaller, the plate area is larger, or a dielectric with a higher permittivity fills the gap. So a small separation between the conductors yields a larger capacitance, allowing more energy to be stored at the same voltage. This is the defining function of a capacitor. In contrast, a resistor wastes energy as heat, an inductor stores energy in a magnetic field from current, and a transistor is a semiconductor device used for switching or amplification, not primarily for storing energy.

The key idea is energy storage in an electric field between two conductors separated by a dielectric. A capacitor does this by having two conductors close together with an insulating material between them. When you apply a voltage, charges accumulate on the plates, creating an electric field in the space between them. The energy is stored in that field, not in the conductors themselves. The amount of energy depends on the capacitance and the voltage, given by U = 1/2 C V^2. Capacitance increases when the separation between the plates is smaller, the plate area is larger, or a dielectric with a higher permittivity fills the gap. So a small separation between the conductors yields a larger capacitance, allowing more energy to be stored at the same voltage. This is the defining function of a capacitor. In contrast, a resistor wastes energy as heat, an inductor stores energy in a magnetic field from current, and a transistor is a semiconductor device used for switching or amplification, not primarily for storing energy.