Energy of a Capacitor
Q. I have a capacitor who’s potential difference between the plates is maintained at 5V using a battery. If the capacitance is 5 F and a dielectric of relative permittivity 3 is placed between the plates such that it fully fills the space, What is the change in energy?
- Increases by 6.24×10−4J
- Decreases by 6.24×10−4J
- Increases by 9.36×10−4J
- Decreases by 9.36×10−4J
Q. The Electric Field between the capacitor plates is a constant 5N/C. If the region between the plates has vacuum, what is the energy density for the capacitor?
- None of these
Q. A capacitor of capacitance 10 μF is connected to a battery providing a potential difference of 10 V across the capacitor. The energy stored inside the capacitor is?
- 1 mJ
- 5 mJ
Q. The area of the plates of a capacitor is 10 cm2 each and the separation between them is 10 mm. The surface charge density of each facing side is 100 μC/cm2. The energy stored inside the capacitor is?
- None of these
Q. A uniformly charged conducting sphere of radius 9 m has a surface charge density of 10C/m2. What is the energy stored inside the sphere (i.e. from 0-R)?
Q. A parallel plate air capacitor is connected to a battery. If plates of the capacitor are pulled further apart, then which of the following statements are correct?
- Strength of electric field inside the capacitor remain unchanged, if battery is disconnected before pulling the plate.
- Potential energy in the capacitor decreases if the battery is disconnected before pulling plates apart.
- Potential energy in the capacitor decreases if the battery remains connected during pulling plates apart.
- During the process, work is done by an external force applied to pull the plates whether battery is disconnected or it remain connected.
Q. The work done in placing a charge of 8×10−18 coulomb on a condenser of capacity 100 micro-Farad is:
Q. When we say that a capacitor with at a certain potential and charges on the plates has a certain amount of energy, what do we mean?
- The charges on the capacitor radiate energy.
- A capacitor with a potential difference across its plates has kinetic energy.
- None of these.
- An external agent like a battery does work which is stored as the potential energy of the charges on the capacitor.
The capacity of a condenser is 4x10-6 farad and its potential is100 volts. The energy released on discharging it fully will be
Q. Change Q on a capacitor varies with voltage V as shown in the figure, where Q is taken along the X-axis and V along the Y-axis. The area of triangle OAB represents
- Capacitive reactance
Magnetic field between the plates
- Energy stored in the capacitor