An ideal solenoid of length 10 cm consists of a wire wrapped tightly around a wooden core. The magnetic field strength is $4.0 \mathrm {~T}$ inside the solenoid. If the solenoid is stretched to 25 cm by applying a force to it, what does the magnetic field become?
A) 1.6 T
B) 10.0 T
C) 20 T
D) 4.0 T

Question

Quizplus · Accepted Answer

The magnetic field inside an ideal solenoid is directly proportional to the number of turns per unit length. Stretching the solenoid increases its length, reducing the number of turns per unit length, and thus the magnetic field strength decreases. The new field strength is calculated by the ratio of the original and new lengths: $ (10/25) \times 4.0 \, \text{T} = 1.6 \, \text{T} $.

An Ideal Solenoid of Length 10 Cm Consists of a Wire