P32_026

# P32_026 - is less than R we solve µ ε r 2 dE dt = µ ε R...

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26. Let R be the radius of a capacitor plate and r be the distance from axis of the capacitor. For points with r R , the magnitude of the magnetic ±eld is given by B = µ 0 ε 0 r 2 dE dt , and for r R ,itis B = µ 0 ε 0 R 2 2 r dE dt . The maximum magnetic ±eld occurs at points for which r = R , and its value is given by either of the formulas above: B max = µ 0 ε 0 R 2 dE dt . There are two values of r for which B = B max / 2: one less than R and one greater. To ±nd the one that
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Unformatted text preview: is less than R , we solve µ ε r 2 dE dt = µ ε R 4 dE dt for r . The result is r = R/ 2 = (55 . 0 mm) / 2 = 27 . 5 mm. To ±nd the one that is greater than R , we solve µ ε R 2 2 r dE dt = µ ε R 4 dE dt for r . The result is r = 2 R = 2(55 . 0 mm) = 110 mm....
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