P15.2 Magnetic fields of electric currents Flashcards
What happens when an electric current passes along a wire?
A magnetic field is set up around the wire
What is the structure of the lines of force along a straight current carrying wire?
Concentric
Why is it important to use a wooden stand and not a metal stand?
Because non-ferrous objects eliminate magnetism caused by nearby iron objects
What is the corkscrew rule?
Associates the direction of an electric current with the direction of the magnetic force lines circling the current
What is a Solenoid?
A long coil of insulated wire
Why are solenoids used?
Where a strong magnetic fields needs to be produced
What happens if the current increases?
Increases the strength of the magnetic field
What happens if the current is reversed
The magnetic field reverses its direction
What is it like inside the solenoid?
It is strong
Uniform
The field lines are parallel to the axis of the solenoid
What are the differences between the magnetic field outside of a bar magnet and a solenoid?
Solenoid has a complete loop unlike bar magnets
How can you identify the polarity of each end of the solenoid from the direction of the current?
S pole is at the end where current is clockwise
N pole is the end at which the current is anticlockwise
What is an electromagnet?
It is a solenoid in which the insulated wire is wrapped around an iron bar( the core)
How does an electromagnet work?
When a current is passed along a wire, a magnetic field is created around the wire
Because of this the magnetic field of the wire magnetises the iron bar
When the current is switched off - the iron bar loses most of its magnetism
