An insulated copper wire is wound on a soft iron core. Current is passed through the coil such that at end A the current flows anti-clockwise and a magnetic compass needle is placed at other end B of the coil.
a) What polarity is created at B?
b) How is the magnetic compass affected when current flows through the coil?
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Solution
A coil of wire which is designed to generate a strong magnetic field within the coil is called a solenoid.
Wrapping the same wire many times around a cylinder creates a strong magnetic field when an electric current is passed through it.
When the fingers of the right hand are curled in the direction of the current flow, the thumb indicates the direction of the magnetic field generated inside the coil.
In the given situation, we can know that the current flows anti-clockwise at the end A. By curling the fingers of the right hand in that manner at the same end, we observe that the thumb points to the end A.
We can mark end A as the north pole and B as the south pole.
a) From the above observations, the polarity created at B is south.
b) The north pole of the compass points to the end A when it is placed near the solenoid.
