Energy stored in a capacitor
- A capacitor of capacitance C = 900 pF is charged fully by 100 V battery B as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance C = 900 pF as shown in figure (b). The electrostati… Answer: 4. 2.25 × 10⁻⁶ J Initial charge: Q=CV=900×10⁻¹²×100=9×10⁻⁸\ C . After connecting to an identical uncharged capacitor, charge is cons... 1
- A parallel plate capacitor has a uniform electric field 'E' in the space between the plates. If the distance between the plates is 'd' and the area of each plate is 'A', the energy stored in the capacitor is : (ε_0 = permittivity of free space) Answer: 3. 1/2ε₀E²Ad Key idea: energy density in an electric field is 1/2ε₀E² ; multiply by the volume between the plates. U=1/2ε₀E²× Ad . O... 1
- A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system : Answer: 1. decreases by a factor of 2 Key idea: charge is conserved when the second capacitor is connected, but energy is not. Initially U=Q... 1
- A capacitor of 2\ μ F is charged as shown in the diagram. When the switch S is turned to position 2, the percentage of its stored energy dissipated is : Answer: 4. 80% Key idea: charge is conserved; it is shared between the capacitors until the potentials are equal, and the difference in ener... 1