41.

Pick out the wrong statement among the following.

• Time varying magnetic field creates an electric field

• Charges in motion can exert force on a stationary magnet

• Stationary charges can exert torque on a stationary magnet

• A bar magnet in motion can exert force on a stationary charge

If a magnet is plugged into a coil, then the magnitude of induced emf does not depend upon

• the number of turns in the coil

• the medium of the core of the coil

• the resistance of the coil

• the strength of the magnet

Identify the wrong statement.

• Current loop is equivalent to a magnetic dipole

• Magnetic dipole moment of a planar loop of area A carrying current I is I²A

• Particles like proton, electron carry an intrinsic magnetic moment

• The current loop (magnetic moment m) placed in a uniform magnetic field, B experiences a torque ζ = m x B

A single turn circular coil is connected to a cell as shown in figure. Magnetic field at the centre O of the coil is

• $\frac{2\mathrm{\pi l}}{\mathrm{r}}$

• $2\mathrm{\pi lr}$

• zero

• $\frac{\mathrm{l}}{2\mathrm{\pi r}}$

A proton is travelling along the x-direction with velocity 5 x 10⁶ ms^-1.The magnitude of force experienced by the proton in a magnetic field $\mathrm{B} = \left(0.2 \hat{\mathrm{i}} + 0.4 \hat{\mathrm{k}}\right)$ tesla is

• 3.2 × 10^-13 N

• 5.3 × 10^-13 N

• 3.2 × 10¹³ N

• 6.3 × 10^-13 N

The shunt required to send 10% of the main current through a moving coil galvanometer of resistance 99 Ω is

• 99 Ω

• 9.9 Ω

• 11 Ω

• 10 Ω

Two identical coils of 5 turns each carry 1 A and 2 A current respectively. Assume that they have common centre with their planes parallel to each other. If their radius is 1 m each and the direction of flow of current in the coils are in opposite directions, then the magnetic field produced on its axial line at a distance of $\sqrt{3}$ m, from the common centre is (in tesla)

• 0

• $\frac{15}{16} {\mathrm{\mu }}_0$

• $\frac{8}{16} {\mathrm{\mu }}_0$

• $\frac{5}{16} {\mathrm{\mu }}_0$

The ratio of the magnetic fields produced at the centre of a solenoid for a flow of current 1 A to that produced inside toroid for the flow of current 2 A both having same number of turns per unit length is

• 1 : 1

• 1 : 2

• 2 : 1

• 1 : 4

Two long parallel wires carrying equal currents which are 8 cm apart produce a magnetic field of 200 µT mid way between them. The magnitude of the current in each wire is

• 10 A

• 20 A

• 300 A

• 40 A

The magnitude of the magnetic field inside a long solenoid is increased by

• decreasing its radius

• decreasing the current through it

• increasing its area of cross-section

• introducing a medium of higher permeability