A solenoid of length 10 cm has 247 turns and a magnetic field at the center of 1.2 T. What is the current through the solenoid?

386.6 A

Explanation:

We are given;

Solenoid length; L = 10 cm = 0.1 m

Number of turns; N = 247

Magnetic field; B = 1.2 T

Now, at the centre of a long solenoid of N turns/metre carrying a current(I), the formula for the magnetic field is given as;

B = μ_oNI/L

Making I the subject we have;

I = BL/μ_oN

Where μ_o is the vacuum of permeability and has a constant value of 4π × 10^(−7) H/m

Thus;

I = (1.2 × 0.1)/(4π × 10^(−7) × 247)

I = 386.6 A

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

are there answer choices to this question? this seems like a question where you have options to choose from.