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Electromagnetic Testing

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Q.3.4 The inductance of a multilayer air core coil with the dimensions I = 0.2,<br />

r = 0.5, b = 0.1 and N = 20, is:<br />

L = 0.8(rN) 2 ∙ (6∙r+9∙l+10∙b) -1 μHenry<br />

A. 1.38 H.<br />

L = self inductance in μH<br />

B. 13.8 μH.<br />

N = number of turns<br />

C. 13.8 ohms.<br />

r = mean radius in inches<br />

l = length of coil in inches<br />

D. 1.38 ohms.<br />

b = coil depth<br />

Q.3.5 The inductive reactance of the coil in Q.3.4, operating at 400 kHz,<br />

would be:<br />

A. 1380 ohms.<br />

X L = 2πfL = (2π∙400∙10 3 ∙13.8∙10 -6 )<br />

B. 5520 ohms.<br />

C. 34.66 ohms.<br />

D. 3466 oluns.<br />

Q.3.6 The impedance of a 100μH coil with a resistance of 20 ohms operating<br />

at 100kHz would be:<br />

A. 62.8 ohms.<br />

X L = 2πfL, Z =√(X L2 + R 2 )<br />

B. 4343.8 ohms.<br />

C. 628 ohms.<br />

D. 65.9 ohms.<br />

Charlie Chong/ Fion Zhang

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