A parallel-plate capacitor has closely spaced circular plates of radius R = 2.00 cm.Charge is flowing onto the positive plate at the rate I = dQ/dt = 1.36 A.The magnetic field at a distance r = 2.00 cm from the axis of the plates is approximately
A)136 mT
B)256 mT
C)16.5 mT
D)457 mT
E)88.3 mT

Question

Quizplus · Accepted Answer

The magnetic field at a distance r from the axis of a parallel-plate capacitor is given by:$$B = \frac{\mu_0}{4\pi} \frac{2I}{r}$$where:* B is the magnetic field in teslas (T)* μ0 is the permeability of free space (4π × 10^-7 T·m/A)* I is the current in amperes (A)* r is the distance from the axis of the capacitor in meters (m)Plugging in the given values, we get:$$B = \frac{(4\pi 	imes 10^{-7} 	ext{ T}\cdot	ext{m/A})(2	imes 1.36 	ext{ A})}{0.02 	ext{ m}} = 136 	ext{ mT}$$Therefore, the correct answer is A.

A Parallel-Plate Capacitor Has Closely Spaced Circular Plates of Radius