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NEET 2012

Exam: NEET
Year: 2012
Subject: Physics
Chapter: Electromagnetic Induction

NEET 2012 · Physics · Electromagnetic Induction

A coil of resistance 400 is placed in a magnetic field. If the...

A coil of resistance

400 \Omega

is placed in a magnetic field. If the magnetic flux

\phi(\mathrm{Wb})

linked with the coil varies with time

t

(sec)

as \phi=50 t^2+4

The current in the coil at

t=2 \mathrm{~s}

is

Options

A $0.5 \mathrm{~A}$
B $0.1 \mathrm{~A}$
C $2 \mathrm{~A}$
D $1 \mathrm{~A}$

Correct answer

A. $0.5 \mathrm{~A}$

Step-by-step solution

Induced emf of coil

E=\left|-\frac{d \phi}{d t}\right|_t

Given,

\phi=50 t^2+4

and

R=400 \Omega

\begin{aligned} E & =\left|-\frac{d \phi}{d t}\right|_{t=2} \\ & =|100 t|_{t=2}=200 \mathrm{~V} \end{aligned}

Current in the coil

\begin{aligned} i & =\frac{E}{R}=\frac{200}{400} \\ & =\frac{1}{2}=0.5 \mathrm{~A} \end{aligned}

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