Q149 / 170 · Manipal (MET) 2020 · Physics

Two coils have mutual inductance of 1.5 H . If current in primary coil is suddenly raised to 5 A in one milli second, the induced emf in the secondary coil is

  • A
    75 V
  • B
    750 V
  • Correct answer
    C
    7500 V
  • D
    75000 V

Solution

Magnetic flux linked with the secondary due to current in the primary. $\phi_2=M I_1$ $\Rightarrow \quad \frac{d \phi_2}{d t}=M \frac{d l_1}{d t}$ $\Rightarrow$ Induced emf in the secondary $\varepsilon_2=\frac{d \phi_2}{d t}=M \frac{d l_1}{d t}$ where, $M=$ mutual inductance $=15 \mathrm{H}$ $\frac{d l_1}{d t}=\frac{5}{1 \times 10^{-3}}=5000 \mathrm{~A} / \mathrm{s}$ $\therefore \quad \varepsilon_2=-1.5 \times 5000 \mathrm{~V}$ $=7.5 \times 1000 V=7500 \mathrm{~V}$

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

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