A parallel-plate capacitor is charged to a potential V0, charged Q0 an...
Initial charge on the plates and potential difference between the plates are Q
0 and V
0 respectively. So, the electrostatic energy is stored inside the capacitor is
Now, if we reduce tlie separation between two plates by a factor 1/2 keeping charge fixed, tlie potential difference two plates wil be
Tlierefore, the final electrostatic energy is stored inside the capacitor is,
Therefore, the charge of electrostatic energy;
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A parallel-plate capacitor is charged to a potential V0, charged Q0 an...
The Change in Electrostatic Energy of a Parallel-Plate Capacitor
Given Information:
- A parallel-plate capacitor is charged to a potential V0 and charge Q0.
- The capacitor is then disconnected from the battery.
- The separation of the plates is halved.
Explanation:
1. Definition of Electrostatic Energy:
- The electrostatic energy of a capacitor is given by the formula: U = (1/2)CV^2, where U is the energy, C is the capacitance, and V is the potential difference across the capacitor.
2. Capacitance of a Parallel-Plate Capacitor:
- The capacitance of a parallel-plate capacitor is given by the formula: C = εA/d, where ε is the permittivity of the medium between the plates, A is the area of each plate, and d is the separation between the plates.
3. Relationship between Charge, Potential Difference, and Capacitance:
- The charge on a capacitor can be expressed as: Q = CV, where Q is the charge, C is the capacitance, and V is the potential difference across the capacitor.
4. Initial Energy of the Capacitor:
- The initial energy of the capacitor can be calculated using the formula: U0 = (1/2)C0V0^2, where U0 is the initial energy, C0 is the initial capacitance, and V0 is the initial potential difference.
5. Relationship between Capacitance and Separation:
- The capacitance of a parallel-plate capacitor is inversely proportional to the separation between the plates. Therefore, when the separation is halved, the capacitance doubles.
6. New Capacitance of the Capacitor:
- After the separation is halved, the new capacitance can be calculated using the formula: C' = εA/(d/2) = 2εA/d = 2C0.
7. New Potential Difference of the Capacitor:
- The charge on the capacitor remains constant, so the new potential difference can be calculated using the formula: V' = Q/C' = Q/(2C0) = V0/2.
8. New Energy of the Capacitor:
- The new energy of the capacitor can be calculated using the formula: U' = (1/2)C'V'^2 = (1/2)(2C0)(V0/2)^2 = (1/2)(C0)(V0^2/4) = (1/8)(C0)(V0^2) = (1/8)U0.
9. Change in Electrostatic Energy:
- The change in electrostatic energy can be calculated by subtracting the new energy from the initial energy: ΔU = U' - U0 = (1/8)U0 - U0 = -(7/8)U0 = -0.875U0.
10. Rounding Off the Answer:
- Rounding off the change in electrostatic energy to two decimal places gives -0.88U0.
Conclusion:
- The change in electrostatic energy, rounded off to two decimal places, is -0