Solenoid → is a long piece of wire wound in a coil.
- some solenoids have a soft iron core → to enhance the strength of magnetic field.
current carrying solenoid → is an electromagnet. when current is passed through solenoid → resultant magnetic field is similar to a bar magnet is generated.
to understand how magnetic field is formed → consider magnetic field from each turn of the coil.
Field lines of each individual turn → add up to give resultant magnetic field.
- since resultant magnetic field is the vector sum of the magnetic field lines of each individual turn → strength of magnetic field can be increased by increasing number of turns.
- strength of the magnetic field depends on the number of turns per unit length, or the number of turns for every metre of the solenoid.
If current flowing thru solenoid is increased → strength of magnetic field of each individual turn would increase.
- this increases resultant strength of magnetic field.
Placing a soft iron core within solenoid → also helps to increase strength of magnetic field.
- this is because soft iron core → tends to concentrate magnetic field.
- this strengthens the field since the field lines are much closer together.
Definition
Strength of magnetic field in solenoid can be increased by:
- increasing the current flowing through the solenoid
- increasing number of turns per unit length of solenoid
- placing a soft iron core within the solenoid