Question

a)A small conducting ring is placed inside a solenoid and is concentric with the axis of the solenoid. If the current in the solenoid changes direction, explain what happens to the magnetic flux through the ring.

b)Explain how a uniform magnetic field (one constant in magnitude and direction) can be created.

Answer 1

(a) When the reversal of current takes place the magnetic flux inside the solenoid which is also passing through the ring changes its direction as the current direction is reversed. The explaination to this effect can be understood using "Right hand thumb rule". It states that if the thumb finger points the direction of the current flow then the remaining fingers when closed represents the direction of magnetic field around the conductor.

Therefore, as the current direction is reversed the magnetic flux passing through the ring is also reversed.

(b) We can't create a perfect uniform magnetic filed, but we can create a nearly uniform magnetic field using a solenoid. If we see a solenoid the core represents a core of a magnet where magnetic flux lines are parallel, constant in magnitude and direction.

Therefore, a large solenoid when excited using a DC current produces a uniform magnetic field which is constant in magnitude as well as in direction at the core of the solenoid.