Q170 / 200 · Manipal (MET) 2012 · Physics

The current in a coil changes from 0 to 2 A in 0.05 s . If the induced emf is 80 V , the self-inductance of the coil is,

  • A
    1 H
  • B
    0.5 H
  • C
    1.5 H
  • Correct answer
    D
    2 H

Solution

From the formula, $\varepsilon=-L \frac{d I}{d t}$ Take magnitude on both sides. $\begin{array}{ll} & |\varepsilon|=\left|-L \frac{d I}{d t}\right| \text { or } \varepsilon=L \frac{d I}{d t} \\ \therefore & 80=L\left(\frac{2}{0.05}\right) \Rightarrow 80=L \times 40 \\ \Rightarrow & L=\frac{80}{40} \Rightarrow L=2 \mathrm{H} \end{array}$

Hence, the correct answer is option: 'D'.

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