What increases the amount of charge a capacitor can store?

What increases the amount of charge a capacitor can store?

• A. Conductor
• B. Dielectric
• C. Vacuum
• D. Insulator

Answer: (B)

In a capacitor, the amount of charge it can store at a given voltage depends on its capacitance. Capacitance rises when a dielectric material is placed between the plates because the dielectric increases the effective electric field screening, described by C = ε0 εr A / d. Here εr is the dielectric constant; it is greater than 1 for a dielectric, so inserting one increases C. Since Q = C V, a larger capacitance means more charge can be stored at the same voltage. A vacuum is the baseline (εr ≈ 1), so it doesn’t boost storage. A conductor would short the plates and destroy the capacitor’s ability to store charge, and simply calling something an “insulator” is vague—the key material that boosts storage is a dielectric with a higher dielectric constant.

In a capacitor, the amount of charge it can store at a given voltage depends on its capacitance. Capacitance rises when a dielectric material is placed between the plates because the dielectric increases the effective electric field screening, described by C = ε0 εr A / d. Here εr is the dielectric constant; it is greater than 1 for a dielectric, so inserting one increases C. Since Q = C V, a larger capacitance means more charge can be stored at the same voltage. A vacuum is the baseline (εr ≈ 1), so it doesn’t boost storage. A conductor would short the plates and destroy the capacitor’s ability to store charge, and simply calling something an “insulator” is vague—the key material that boosts storage is a dielectric with a higher dielectric constant.