1. ⇒ (MHT CET 2023 10th May Evening Shift )

A solenoid of 500 turns/m is carrying a current of 3 A. Its core is made of iron which has relative permeability 5001. The magnitude of magnetization is

A. $4.5 \times 10^{6} {Am}^{- 1}$

B. $6.0 \times 10^{- 6} {Am}^{- 1}$

C. $7.5 \times 10^{6} {Am}^{- 1}$

D. $9.0 \times 10^{6} {Am}^{- 1}$

Correct Option is (C)

Given: $n = 500$ turns $/ m, I = 3 A$

$\begin{aligned} μ_{r} = 5001 \\ ∴ μ = n I = 500 \times 3 A \\ = 1500 A / m \\ But, χ_{m} = μ_{r} - 1 \\ = 5001 - 1 \\ = 5000 \\ ∴ Magnetization M = χ_{m} H \\ = 5000 \times 1500 \\ = 7.5 \times 10^{6} {Am}^{- 1} \end{aligned}$

2. ⇒ (MHT CET 2023 10th May Morning Shift )

According to Curie's law in magnetism, the correct relation is ( $M =$ magnetization in paramagnetic sample, $B =$ applied magnetic field, $T =$ absolute temperature of the material, $C =$ curie's constant)

A. $M = \frac{T}{CB}$

B. $M = \frac{C B}{T}$

C. $C = \frac{MB}{T}$

D. $C = \frac{T^{2}}{MB}$

Correct Option is (B)

Currently no explanation available

3. ⇒ (MHT CET 2023 9th May Evening Shift )

A thin rod of length $L$ has magnetic moment $M$ when magnetised. If rod is bent in a semicircular arc what is magnetic moment in new shape?

A. $\frac{M}{L}$

B. $\frac{M}{π}$

C. $\frac{M}{2 π}$

D. $\frac{2 M}{π}$

Correct Option is (D)

Magnetic moment of $rod = M$

Let $r$ be the radius after bending it into a semicircular arc.

$∴$ The separation between the two ends is $2 r$ . Here length $=$ circumference of the semicircle i.e., $L = π r$

$∴ r = \frac{L}{π}$

Also $M = m \times L$ and $m = \frac{M}{L}$

$\begin{aligned} ∴ M_{new} = m (2 r) & = \frac{M}{L} \times \frac{2 L}{π} \\ = \frac{2 M}{π} \end{aligned}$

4. ⇒ (MHT CET 2021 21th September Evening Shift )

The north pole of a long horizontal bar magnet is being brought towards closed circuit consisting of a coil. The direction of induced current produced in it is

A. anticlockwise

B. horizontal

C. vertical

D. clockwise

Correct Option is (A)

According to the Lenz's law, the induced current is such that it opposes the change in flux which causes it. Hence the induced current produces a field which opposes the field due to the magnet. For this it should flow in anticlockwise direction.

5. ⇒ (MHT CET 2021 21th September Morning Shift )

What is susceptibility of a medium, if its relative permeability is 0.85?

A. 1.85

B. 0.15

C. $- 0.15$

D. $- 0.85$

Correct Option is (C)

Relative permeability $μ_{r} = 1 + χ$

$∴ χ = μ_{r} - 1 = 0.85 - 1 = - 0.15$

⇒Magnetism and Matter