Electromagnetism – Gauss' Law

A uniformly charged sphere of total charge Q expands and contract between radii R1 and R2  at a frequency f. The total power radiated by the sphere is

A. proportional to Q
B. proportional to f2
C. proportional to f4
D. proportional to (R1 / R2)
E. zero
(GR0177 #96)
Solution:

Power, P = VI
I = dq / dt
Q is constant → dq = 0 → I = 0  → P = 0

Answer: E

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