Which device is used to store electric charge?

A capacitor is the device specifically designed to store electric charge. It consists of two conductive plates separated by an insulating material called a dielectric. When a voltage is applied across the capacitor, electric charge accumulates on the plates, creating an electric field. The amount of charge stored is directly proportional to the voltage applied and is determined by the capacitance value of the capacitor.

Capacitors are widely used in various applications, such as in power supply circuits for smoothing out voltage fluctuations, in timing circuits, and in filtering applications to remove unwanted signals.

In contrast, a resistor is used to impede the flow of electric current and dissipate energy as heat rather than storing charge. An inductor is a device that stores energy in a magnetic field, not as electric charge. A transistor functions as a semiconductor device typically used for switching or amplifying electrical signals rather than storing charge. Thus, the capacitor stands out as the correct answer for storing electric charge effectively.