Pulling Apart a Capacitor 1
Consider a simple parallel-plate capacitor whose plates are given equal and opposite charges and are separated by a distance d. Suppose the plates are pulled apart by a scientist with insulating gloves until they are separated by a distance D>d. The electrostatic energy stored in the capacitor is now:
Consider a simple parallel-plate capacitor whose plates are given equal and opposite charges and are separated by a distance d. Suppose the plates are pulled apart by a scientist with insulating gloves until they are separated by a distance D>d. The electrostatic energy stored in the capacitor is now:
A) larger.
A) larger.
B) the same.
B) the same.
C) smaller.
C) smaller.
D) indeterminate.
D) indeterminate.
Solution: A. The capacitance decreases as the plates are separated since distance is in the denominator of the formula for capacitance of a parallel plate capacitor. The charge remains the same due to the insulating gloves. The formula U = Q^2/(2C) indicates that the energy stored in the capacitor increases.
Solution: A. The capacitance decreases as the plates are separated since distance is in the denominator of the formula for capacitance of a parallel plate capacitor. The charge remains the same due to the insulating gloves. The formula U = Q^2/(2C) indicates that the energy stored in the capacitor increases.