JEE Main · 2023 · 24 Jan 2023 · Shift 2 · Magnetic Effects of Current

A long solenoid is formed by winding 70 turns cm

^{- 1}

. If 2.0 A current flows, then the magnetic field produced inside the solenoid is ______ (

μ_{0} = 4 π \times 1 0^{- 7}

TmA

^{- 1}

)

(A) $1232 \times 1 0^{- 4}$ T
(B) $176 \times 1 0^{- 4}$ T✓ Correct
(C) $352 \times 1 0^{- 4}$ T
(D) $88 \times 1 0^{- 4}$ T

Answer: (B)

Solution

Inside a long solenoid the field is uniform and equal to

B = μ_{0} n I

. Here the turn density is

n = 70 turns cm^{- 1} = 7000 turns m^{- 1}

and the current is

I = 2.0

A, so

B = 4 π \times 1 0^{- 7} \times 7000 \times 2 = 5.6 π \times 1 0^{- 3} T

. Evaluating, the magnetic field inside the solenoid is

176 \times 1 0^{- 4} T

JEE Main · 2023 · 24 Jan 2023 · Shift 2 · Single correct option

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