What is a capacitor?

What is a capacitor?

• A. A device storing energy via magnetic fields.
• B. A device made of two conductors separated by a small distance.
• C. A device that converts AC to DC.
• D. A single conductor with insulation.

Answer: (B)

A capacitor stores energy in an electric field created by charges on two conductors that are separated by an insulating material. When connected to a voltage source, opposite charges accumulate on the two plates, building a field in the space between them. The energy you store is in that field, not in any magnetic form. The two conductors are essential—the charges sit on two different surfaces, creating the field across the gap. A single insulated conductor wouldn’t form a capacitor because there’s no second plate to hold opposite charge. How much energy and how easily a capacitor can store charge depend on the plate area, the distance between the plates, and the insulating material (dielectric) between them. Larger plates or a material with a higher dielectric constant increase capacitance, while a smaller gap also increases it. In formula terms, energy stored is proportional to (1/2) C V^2, where C grows with area and dielectric constant and shrinks with increasing separation. This is why capacitors are used for smoothing, timing, and energy storage in circuits.

A capacitor stores energy in an electric field created by charges on two conductors that are separated by an insulating material. When connected to a voltage source, opposite charges accumulate on the two plates, building a field in the space between them. The energy you store is in that field, not in any magnetic form. The two conductors are essential—the charges sit on two different surfaces, creating the field across the gap. A single insulated conductor wouldn’t form a capacitor because there’s no second plate to hold opposite charge.

How much energy and how easily a capacitor can store charge depend on the plate area, the distance between the plates, and the insulating material (dielectric) between them. Larger plates or a material with a higher dielectric constant increase capacitance, while a smaller gap also increases it. In formula terms, energy stored is proportional to (1/2) C V^2, where C grows with area and dielectric constant and shrinks with increasing separation. This is why capacitors are used for smoothing, timing, and energy storage in circuits.