Capacitor energy storage
A charged capacitor stores electrical potential energy. Energy stored E = ½QV = ½CV² = Q²/(2C) where Q is charge, V is potential difference, and C is capacitance.
Formula
E = ½CV² = ½QV = Q²/2C
Real World
Hybrid cars like the Toyota Prius use large capacitor banks alongside batteries to store energy recovered during regenerative braking, releasing it rapidly to assist acceleration where batteries alone would respond too slowly.
Exam Focus
Use E = ½CV² when voltage is given and E = Q²/2C when charge is given — choosing the wrong form wastes time on unnecessary algebra.
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