JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Magnetic Effects of Current

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A solenoid of 1200 turns is wound uniformly in a single layer on a glass tube 2 m long and 0.2 m in diameter. The magnetic intensity at the center of the solenoid when a current of 2 A flows through it is:

(A) $2.4 \times 1 0^{3} A m^{- 1}$
(B) $1.2 \times 1 0^{3} A m^{- 1}$ ✓ Correct
(C) $1 A m^{- 1}$
(D) $2.4 \times 1 0^{- 3} A m^{- 1}$

Answer: (B)

Solution

The magnetising field inside a long solenoid is

H = n I

, with

n

the number of turns per unit length. With

N = 1200

turns over

L = 2 m

n = \frac{1200}{2} = 600 turns m^{- 1}

. For

I = 2 A

this gives

H = 600 \times 2 = 1200 A m^{- 1} = 1.2 \times 1 0^{3} A m^{- 1}

. The diameter does not enter the on-axis field of a long solenoid, so the magnetic intensity at the centre is

1.2 \times 1 0^{3} A m^{- 1}

JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Single correct option

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JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Magnetic Effects of Current

Solution

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