# 19.1.5 Energy Stored in a Capacitor

### Calculating Energy Stored in a Capacitor

• Recall the electric potential energy is the area under a potential-charge graph
• This is equal to the work done in charging the capacitor to a particular potential difference
• The shape of this area is a right angled triangle
• Therefore the work done, or energy stored in a capacitor is defined by the equation:

• Substituting the charge with the capacitance equation Q = CV, the work done can also be defined as:

• Where:
• W = work done/energy stored (J)
• Q = charge on the capacitor (C)
• V = potential difference (V)
• C = capacitance (F)
• By substituting the potential V, the work done can also be defined in terms of just the charge and the capacitance:

#### Worked example: Energy stored in a capacitor

Step 1:            Write down the equation for energy stored, in terms of capacitance C and p.d V

Step 2:            The change in energy stored is proportional to the change in p.d

Step 3:            Substitute in values

### Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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