How does the magnetic field at point P compare with the magnetic field at point Q? Justify your answer.

Question

A helical coil whose length is greater than its diameter is connected to a battery as shown below.

(a) How does the magnetic field at point P compare with the magnetic field at point Q? Justify your answer. 

(b) State one way in which the strength of the magnetic field inside a current carrying helical coil can be changed?

Answer 1

(a) The magnetic field at P and Q is the same, because the magnetic field lines inside the helical coil of wire which behaves like a solenoid is uniform/in the form of parallel straight lines.

(b) increasing/decreasing the number of turn in the coil  

increasing/decreasing the current through the coil