P15.4 The motor effect Flashcards
What is the motor effect?
A current-carrying wire or coil can exert a force on a permanent magnet.
How can the size of the force be increased?
Increasing the current
Using a stronger magnet
How can the size of the force depend on the angle between the wire and the field lines?
The force is greatest when the wire is perpendicular to the magnetic field lines
Zero when the wire is parallel to the magnetic field lines
What is the purpose of Flemming’s left hand-rule?
To work out the direction of the force
Which finger represents what in Flemming’s left hand rule?
First finger represents Field
Second finger represents Current
Thumb represents direction of force
What is the magnetic flux density?
It is the measure of the strength of the magnetic field?
What does the size of a force depend on?
The current
Length
Magnetic flux density
What is the equation for force?
Force = magnetic flux density x current x length Newtons = Tesla, T x Current, A x length, m
How can you control the speed of an electric motor?
By changing the current
How does a motor work?
Current is going in one direction which causes the force to act down in the particular area
Current is going the other direction on the opposite end which causes the force to act up
This is due to the motor effect
What is the purpose of the split - ring commutator?
Reverse the current every half - turn
Becauses the sides swap over each half-turn
The coil is pushed in the same direction
What is the purpose of Graphite being in contact with the rotating commutator?
Conducts electricity and acts as brush to press onto the split - ring commutator which is made up of metal
Why does the coil spin?
A force acts on each side of the coil due to the motor effect
The force on on one side is the opposite direction to the force on the other side
