41.

The magnetic moment of a short bar magnet is 4 Am² . The magnetic induction at a point 10 cm away from its  mid point on axial line is B₁ , and on the equatorial line is B₂ , then

• B₁ = 8 × 10^-4 T , B₂ = 4 × 10^-4 T

• B₁ = 2 × 10^-4 T , B₂ = 1 × 10^-4 T

• B₁ = 10 × 10^-4 T , B₂ = 5 × 10^-4 T

• B₁ = 6 × 10^-4 T , B₂ = 3 × 10^-4 T

The speed of electromagnetic waves in vaccum is

• µ₀ε₀

• $\frac{1}{\sqrt{{\mathrm{\mu }}_0{\mathrm{\epsilon }}_0}}$

• $\sqrt{{\mathrm{\mu }}_0{\mathrm{\epsilon }}_0}$

• $\frac{1}{{\mathrm{\mu }}_0{\mathrm{\epsilon }}_0}$

An electromagnetic wave travels along Z- axis. The pair of space and time varying field is

• E_y, B_x

• B_y, E_z

• E_x, B_y

• E_z, B_x

The ratio of inductive reactance to capacitive reactance in an AC circuit will be

• ω LC

• ω² L

• zero

• ω² LC

The magnetic flux through a circuit of resistance R changes by Δ$\mathrm{\varphi }$ in times Δt. Then, the-total amount of  electric charge that passes in any point in the circuit during this time 'Δt' will be

• $\mathrm{Q} = \frac{∆\mathrm{\varphi }}{\mathrm{R}}$

• $\mathrm{Q} = ∆\mathrm{\varphi } . \mathrm{R}$

• $\mathrm{Q} = \frac{\mathrm{R}∆\mathrm{t}}{∆\mathrm{\varphi }}$

• $\mathrm{Q} = ∆\mathrm{t} . \mathrm{R}$

The value of angle of dip is zero at the magnetic equator because on it

• V and H are equal

• the value of V is zero

• the value of H is zero

• the value of V is infinity

In a step up transformer, the turns ratio of field is primary and secondary is 1 : 4. A  leclanche cell of emf 1.5 V is connected across the primary. The voltage developed across the secondary will be

• 3 V

• 6 V

• 1 V

• zero

A thermister is dipped in a water bath. As the temperature increases the current in the thermistor also increases. This is due to decrease in

• resistivity

• conductivity

• reactance

• capacitance

In an AC circuit, voltage and current are given by V = 50 sin (lO0 t) V and I = 50 sin $\left(100 \mathrm{t} + \frac{\mathrm{\pi }}{3}\right)$ A. The power dissipiated in the circuit is

• 125 W

• 625 W

• 1250 W

• 100 W

The magnetic flux in a closed circuit of resistance 10 Ω varies with time t (in second) as $\mathrm{\pi }$ = (4t² − 5t + 1)Wb. The magnitude of induced current at t = 0.20 s is

• 0.12 A

• 0.38 A

• 0.34 A

• 0.12 A