Question

Show with the aid of a diagram how a wire is wound on a U-shaped piece of soft iron in order to make it an electromagnet. Complete the circuit diagram and label the poles of the electromagnet.

Answer 1

An electromagnet is simply a coil of wire. It is usually wound around an iron core. However, it could be wound around an air core, in which case it is called a solenoid. When connected to a current source, the electromagnet becomes energized, creating a magnetic field just like a permanent magnet. The magnetic flux density is proportional to the magnitude of the current flowing in the wire of the electromagnet.
The polarity of the electromagnet is determined by the direction the current. The north pole of the electromagnet is determined by using our right hand. If we wrap our fingers around the coil in the same direction as the current is flowing (conventional current flows from + to -). The direction our thumb is pointing is the direction of the magnetic field, so north would come out of the electromagnet in the direction of our thumb.
Above is the circuit diagram of an electromagnet on a horse shoe shaped core with the poles marked and direction of current indicated.