The motor effect (HT only) Flashcards
State the direction that current flows in a circuit
Positive to negative
State the direction of the magnetic field around a bar magnet
North to south
Explain what is meant by magnetic flux density.
Magnetic field strength
Describe the motor effect
When a current is passed along a wire in a magnetic field a force is exerted on the wire by the magnetic field.
What do the fingers stand for in Fleming’s left hand rule?
Thumb- force, first finger- field, second finger- current
What direction must the wire be in relation to the magnetic field in order to experience a force
Perpendicular (if it is parallel it will not experience a force)
State the factors that affect the size of a force on a current carrying wire
Magnetic field strength, current, length of wire
Explain what is meant by magnetic flux density
Magnetic field strength
State the units magnetic flux density is measured in
Tesla (T)
Write the equation that links magnetic field strength, force, length of wire and current
Force = magnetic field strength x current x length of the wire
Describe how a loudspeaker uses the motor effect to make sound waves from electrical signals
Alternating current through coil in magnetic field -> Causes force on coil -> it moves back and forth -> Causes air particles to oscillate -> sound wave
Define the term DC
Direct current- current that flows in one direction
List the main components of a DC motor
Permanent magnet, coil of wire, split ring commutator, DC power supply
Explain what causes a force on a wire
Current through the coil of wire produces a magnetic field which interacts with the magnetic field of the permanent magnet
Explain why there are opposite forces on each side of the coil
The current flows in the opposite direction on each side of the coil
