**Exercise 19.45**

Part A = to the right

Part B = 0.063 T

**Solutions Below:**

Part A

The magnetic field in a solenoid is:

B = μ_{0} * I * n

Where μ_{0} is the magnetic constant, I is the current, and n is the number of coils per meter.

Since the solenoid in this problem has two layers, find the larger of the two magnetic fields and just use the right hand rule to determine the direction. See Part B for more info.

to the right

Part B

Express your answer using two significant figures.

The magnetic field in a solenoid is:

B = μ_{0} * I * n

Where μ_{0} is the magnetic constant, I is the current, and n is the number of coils per meter. Since the solenoid in this problem has two layers, just take the difference, which will give you the magnitude of the magnetic field.

Find the magnetic field from the inner layer:

B_{inner} = 1.2566*10^-6 * 10 * 25000

B_{inner} = 0.31415

Now find the magnetic field from the outer layer:

B_{outer} = 1.2566*10^-6 * 15 * 20000

B_{outer} = 0.37698

Take the difference to find the overall magnetic field:

0.063 T