A closely wound solenoid 80 cm long has 5 layers of 400 turns each and…

Question

A closely wound solenoid 80 cm long has 5 layers of 400 turns each and carries a current of 8.0 A. The magnitude of B near its centre is approximately:

Accepted Answer

B. 2.5 × 10⁻² T

1. Total turns: $N = 5	imes400 = 2000$.
2. Turns per unit length: $n = \dfrac{2000}{0.80} = 2500$ m⁻¹.
3. Inside field: $B = \mu_0 n I = 4\pi	imes10^{-7}	imes2500	imes8.0$.
4. $B = 4\pi	imes10^{-7}	imes2	imes10^{4} = 8\pi	imes10^{-3}$.
5. $B \approx 2.5	imes10^{-2}$ T.
_Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", p.158_

Answer

2.5 × 10⁻³ T

Answer

5.0 × 10⁻² T

Answer

1.3 × 10⁻² T