Question

There are 50 turns/cm in a long solenoid. If 4 Amp current is flowing in the solenoid, the approximate value of mag. field along its axis at an internal point and one end will be respectively.

(a) 12.6 × 10^–3 Tesla; 6.3 × 10^–3 tesla

(b) 12.6 × 10^–3 Tesla ; 25.1 × 10^–3 tesla

(c) 25.1 × 10^–3 Tesla ; 12.6 × 10^–3 tesla

(d) 25.1 × 10^–5 Tesla ; 6.3 × 10^–5 tesla

Answer 1

 The correct option (c) 25.1 × 10^–3 Tesla ; 12.6 × 10^–3 tesla

Explanation:

n = 50 (turns/cm) = 5000 (turns/meter)

I = 4A

B_inside = μ₀nI

B_end = [(μ₀nI)/2][sin0 + sin90] = [(μ₀nI)/2]

For the solenoid,

∴   B_inside = μ₀nI

= 4π × 10^–7 × 5000 × 4

= 25.1 × 10^–3T

B_end = (1/2) × B_inside = 12.5 × 10^–3T