A solenoid is wound with 290 turns per centimeter. An outer layer of insulated wire with 200 turns per centimeter is wound over the solenoid's first layer of wire. When the solenoid is operating, the inner coil carries a current of 10 A and the outer coil carries a current of 15 A in the direction opposite to that of the current in the inner coil.

Question

What is the direction of the magnetic field at the center for this configuration?
a)upward
b)downward
c)to the left
d)to the right

What is the magnitude of the magnetic field at the center of the doubly wound solenoid?
B= T

Answer 1

Without a figure, we have no way to relate up, down, left and right to the configuration and orientation of the solenoid.

There should be a formula for the magnetic field inside a solenoid in your textbook.

Answer 2

Downward