Lecture 22, ACT 1

• Suppose at time t, the currents flowing into C and 2C are identical and that 2C has twice the area of C as shown. Compare the magnetic fields at the points shown BI(ro/2) and BII(ro/2):

(a) BI < BII

(b) BI = BII

(c) BI > BII

• If the currents flowing to the capacitors are equal, the total displacement currents are also equal.

• The displacement currents are distributed uniformly throughout the volume between the two plates.

• Therefore, when we apply our new form of Ampere’s Law to find the magnetic field, the fraction of the displacement current with r<ro/2 is smaller in case II than it is in case I. Therefore, BII < BI.
  • Here are the equations behind these words:

ro/2

ro

I

I

ro/2

I

II

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