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Electromagnetic Induction

Multiple Choice Questions

91.

A coil of inductance 8 μH is connected to a capacitor of capacitance 0.02 μF To what wavelength is this circuit tuned?

7.54 × 10³ m
4.12 × 10² m
15.90 × 10³ m
7.54 × 10² m

92.

Assertion: An emf E is induced in a closed loop when magnetic flux is varied. The induced electric field E is not a conservative field.

Reason: The line integral $\oint \bar{E} \cdot \bar{dl}$ around the closed loop is non-zero.

If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

93.

The most suitable metal for making electromagnets and transformer cores is

steel
iron
copper
aluminium

94.

Which of the following is the best method to reduce eddy currents?

Laminating core
Using thick wires
Reducing hysteresis loss
None of these

95.

Two solenoids of equal number of turns having their length and the radii in the same ratio 1:2. The ratio of their self-inductance will be

96.
An engine has an efficiency of 1/6. When the temperature of sink is reduced by 62^oC, its efficiency is doubled. The temperature of source will be

37^o C

62^o C

99^o C

124^o C

99^o C

η = $1 - \frac{T_{2}}{T_{1}}$

or $\frac{T_{2}}{T_{1}} = 1 - η$

According to first case

$\frac{T_{2}}{T_{1}} = 1 - \frac{1}{6}$

⇒ $\frac{T_{2}}{T_{1}} = \frac{5}{6}$

According to second case

$\frac{T_{2} - 62}{T_{1}} = 1 - 2 \times \frac{1}{6}$

⇒ $\frac{T_{2}}{T_{1}} - \frac{62}{T_{1}} = \frac{2}{3}$

From equations (i) and (ii), we get

$\frac{5}{6} - \frac{62}{T_{1}} = \frac{2}{3}$

⇒ $\frac{T_{2}}{T_{1}} - \frac{62}{T_{1}} = \frac{2}{3}$

From equations (i) and (ii), we get

$\frac{5}{6} - \frac{62}{T_{1}} = \frac{2}{3}$

⇒ $\frac{5}{6} - \frac{2}{3} = \frac{62}{T_{1}}$

⇒ $\frac{1}{6} = \frac{62}{T_{1}}$

T₁ = 372 K

⇒ T₁ = 372 - 327

⇒ T₁= 99^o C

97.

Mutual inductance M between two concentric coils of radii 1 m and 2 m is

$\frac{μ_{0} π}{2}$
$\frac{μ_{0} π}{4}$
$\frac{μ_{0} π}{8}$
$\frac{μ_{0} π}{10}$

98.

Lenz law is consistent with conservation of

Energy
Mass
Charge
Momentum

99.

A circular coil with a cross-sectional area of 4 cm² has 10 turns. It is placed at the center of a long solenoid that has 15 turns/cm and a cross-sectional area of IO cm2, as shown in the figure. The axis of the coil conicides with the axis of the solenoid. What is their mutual inductance?