Electromagnetic Induction | Physics JEE Main questions with Solutions

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Topic Question Set

Q 1 :
In a coil, the current changes from $- 2 A$ to $+ 2 A$ in 0.2 s and induces an emf 0.1 V. The self-inductance of the coil is: [2024]

4 mH
5 mH
2.5 mH
1 MH

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2

3

4

(B) ${(Emf)}_{induced} = - L \frac{d i}{d t}$

In magnitude form,

$| {Emf}_{ind} | = | (-) L \frac{d i}{d t} |$

$\Rightarrow 0.1 = \frac{(L) [+ 2 - (- 2)]}{0.2} \Rightarrow L = \frac{0.1 \times 0.2}{4} = 5 mH$

Q 2 :
The current in an inductor is given by $I = (3 t + 8)$ where $t$ is in second. The magnitude of induced emf produced in the inductor is 12 mV. The self-inductance of the inductor ________ mH. [2024]

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(4) $| \in | = L \frac{d i}{d t}$

$i = | 3 t + 8 | \Rightarrow \frac{d i}{d t} = 3$

$ε = 12 mV$

$| ε | = L | \frac{d I}{d t} | \Rightarrow 12 = L \times 3$

$L = 4 mH$

Q 3 :
Two coils have mutual inductance 0.002H. The current changes in the first coil according to the relation $i = i_{0} \sin ω t$ , where $i_{0} = 5 A$ and $ω = 50 π$ rad/s. The maximum value of emf in the second coil is $\frac{π}{α}$ V. The value of $α$ is _____. [2024]

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(2) $ϕ = M i = M i_{0} \sin ω t$

$EMF = - M \frac{d i}{d t} = - 0.002 (i_{0} ω \cos ω t)$

${EMF}_{\max} = i_{0} ω (0.002) = (5) (50 π) (0.002)$

${EMF}_{\max} = \frac{π}{2} V$

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