PhysicsChapter 5: Electric Potential and Capacitor
Energy Stored in A Capacitor
The energy stored in a capacitor
Definition
The energy stored in a capacitor is the electric potential energy required to separate charge onto its plates.
Energy Density
As a capacitor charges, its voltage rises from zero to final value `V`. For charge `q` at an intermediate stage: V=qC Small work: dU=Vdq Therefore: dU=(qC)dq Integrating from `0` to final charge `Q`: U=Q²2C Since: Q=CV equivalent forms are: U=½QV U=½CV² U=Q²2C For an electric field in vacuum: **u = ½ε₀E²** where `u` is energy per unit volume.
Formula / Key Relation
**U=½QV U=½CV² U=Q²2C**
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Energy Stored in A Capacitor
Sticky Notes · Quick Revision
CAPACITOR ENERGY
- `½QV`
- `½CV²`
- `Q²/2C`
60-second revision
- Energy is stored in the capacitor's electric-field configuration.
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