Multiple choice

The magnetic flux through a loop of resistance 0.1Ω is varying according to the relation ø = 6 t 2 + 7 t + 1 where ø is in milli Wb and t is in seconds. What is the e.m.f. induced in the loop at t = 1 s and the magnitude of the current?

  1. 9 mV, 190 mA

  2. 130mV, 130 mA

  3. 13mV, 1.3 mA

  4. 19mV, 5.2 A

  5. 19mV, 1.9 mA
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A Correct answer
Explanation

R = 0.1 Ω; ø = 6 t2+ 7 t + 1 ; t = 1 s; e = ? I = ? e = dø/dt = 6 x 2 t + 7 = 12 t + 7 ∴At t = 1, e = 12 + 7 = 19 mV Now I = e / R= 19 x 10-3/ 0.1 = 19 x 10-2 = 190 mA.

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