NEET PYQ: Electromagnetic Induction Chapter-Wise Questions

Q 1 :
A big circular coil of 1000 turns and average radius 10 m is rotating about its horizontal diameter at 2 $rad$ $s^{- 1}$ . If the vertical component of earth’s magnetic field at that place is $2 \times 10^{- 5} T$ and electrical resistance of the coil is 12.56 $Ω$ , then the maximum induced current in the coil will be [2022]

0.25 A
1.5 A
1 A
2 A

1

2

3

4

(3)

Given, number of turns $(N) = 1000$

Radius $(r) = 10$ $m$

Angular velocity $(ω) = 2$ $rad$ $s^{- 1}$

Magnetic field $(B) = 2 \times 10^{- 5} T$

Electrical resistance $(R) = 12.56 Ω$

Maximum induced emf $= N ω A B$

Here area of the circular coil $A = π r^{2}$

$ε = N ω π r^{2} B = 1000 \times 2 \times 3.14 \times {(10)}^{2} \times 2 \times 10^{- 5}$

$ε = 12.56 V$

The maximum induced current is, $i_{max} = \frac{ε}{R}$

$\Rightarrow i_{max} = \frac{12.56}{12.56} = 1$ $A$

Q 2 :
A 800 turn coil of effective area 0.05 $m^{2}$ is kept perpendicular to a magnetic field $5 \times 10^{- 5} T$ . When the plane of the coil is rotated by $90 °$ around any of its coplanar axis in 0.1 $s$ , the emf induced in the coil will be [2019]

0.02 V
2 V
0.2 V
$2 \times 10^{- 3} V$

1

2

3

4

(1)

Here $N = 800,$ $A = 0.05$ $m^{2},$ $Δ t = 0.1$ $s$

$B = 5 \times 10^{- 5} T$

Induced emf, $ε = - \frac{Δ ϕ}{Δ t} = - \frac{(ϕ_{f} - ϕ_{i})}{Δ t}$

$ϕ_{i} = N (\vec{B} \cdot \vec{A}) = 800 \times 5 \times 10^{- 5} \times 0.05 \times \cos 0 ° = 2 \times 10^{- 3} {Tm}^{2}$

$ϕ_{f} = 0 \Rightarrow ∴$ $ε = \frac{- (0 - 2 \times 10^{- 3})}{0.1} = 2 \times 10^{- 2} V = 0.02$ $V$

Q 3 :
A uniform magnetic field is restricted within a region of radius $r$ . The magnetic field changes with time at a rate $\frac{d \vec{B}}{d t}$ . Loop 1 of radius $R > r$ encloses the region $r$ and loop 2 of radius $R$ is outside the region of magnetic field as shown in the figure. Then the e.m.f. generated is [2016]

zero in loop 1 and zero in loop 2
$- \frac{d \vec{B}}{d t} π r^{2}$ in loop 1 and $- \frac{d \vec{B}}{d t} π r^{2}$ in loop 2
$- \frac{d \vec{B}}{d t} π R^{2}$ in loop 1 and zero in loop 2
$- \frac{d \vec{B}}{d t} π r^{2}$ in loop 1 and zero in loop 2

1

2

3

4

(4)

Emf generated in loop 1,

$ε_{1} = - \frac{d ϕ}{d t} = - \frac{d}{d t} (\vec{B} \cdot \vec{A}) = - \frac{d}{d t} (B A) = - A \times \frac{d B}{d t}$

$ε_{1} = - (π r^{2} \frac{d B}{d t}) (∵ A = π r^{2} because \frac{d B}{d t} is restricted up to radius r .)$

Emf generated in loop 2, $ε_{2} = - \frac{d}{d t} (B A) = - \frac{d}{d t} (0 \times A) = 0$

Topic Question Set

Q 2 :
A 800 turn coil of effective area 0.05 $m^{2}$ is kept perpendicular to a magnetic field $5 \times 10^{- 5} T$ . When the plane of the coil is rotated by $90 °$ around any of its coplanar axis in 0.1 $s$ , the emf induced in the coil will be [2019]

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Topic Question Set

Q 2 : A 800 turn coil of effective area 0.05 m2 is kept perpendicular to a magnetic field 5×10-5T. When the plane of the coil is rotated by 90° around any of its coplanar axis in 0.1 s, the emf induced in the coil will be [2019]

Q 3 : A uniform magnetic field is restricted within a region of radius r. The magnetic field changes with time at a rate dB→dt. Loop 1 of radius R>r encloses the region r and loop 2 of radius R is outside the region of magnetic field as shown in the figure. Then the e.m.f. generated is [2016]

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Q 2 :
A 800 turn coil of effective area 0.05 $m^{2}$ is kept perpendicular to a magnetic field $5 \times 10^{- 5} T$ . When the plane of the coil is rotated by $90 °$ around any of its coplanar axis in 0.1 $s$ , the emf induced in the coil will be [2019]