Fields of Coils and Solenoids
Fields of Coils and Solenoids
- A curved current combines many circular field contributions.
A flat coil and a long solenoid
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- A flat circular coil concentrates the field through its centre.
- A long solenoid has nearly straight, evenly spaced field lines inside, so its internal field is nearly uniform.
- Its outside pattern is like a bar magnet. Field lines leave the north end and enter the south end.
- A ferrous core, such as iron, increases the field.
Find the north end
Curl the fingers of your right hand with the conventional current around the turns. Your thumb points towards the north end and the field inside.
Near geographic North, Earth behaves as a magnetic south pole because it attracts the north end of a compass (9702/42/M/J/25 Q2(b)).
Your turnquick check
State two changes that increase the magnetic field inside a solenoid.
Show worked answer
Increase the current and insert a ferrous core.