Electromagnetism is caused by the magnetic fields around wires carrying an electric current. The induced magnetic field of a wire can interact with other nearby magnets, producing a force.
Which of the following is a way of working out which way the force on a wire will act?
Fleming’s right-hand rule
Fleming’s left-hand rule
The generator rule
What sort of force is generated when the current and the magnetic field are parallel to each other?
No force is generated
Maximum force is generated
Half the maximum force is generated
In Fleming’s left hand rule, which finger represents the current?
The second finger
What are the main components in a loudspeaker?
Coil of wire, split ring commutator, cone
Coil of wire, permanent magnet, cone
Permanent magnet, split ring commutator, cone
How do headphones generate sounds?
They contain small loudspeakers
The headphone wires carry sound waves to the ears
The sounds are generated by the electronic music device, rather than the headphones themselves
Which equation is used to calculate the force on a wire carrying a current at right angles to a magnetic field?
Force on a conductor carrying a current = magnetic flux × length
Force on a conductor carrying a current = magnetic flux density × current × length
Force on a conductor carrying a current = magnetic flux density ÷ current × length
0.4 A flows in 0.1 m of wire in a 0.7 T magnetic field. What force acts on the wire?
In a dc motor, what is the function of the split ring commutator?
It reverses the current direction every half turn, to keep the motor spinning in the same direction all the time
It shields the magnetic field from acting outside the motor case
It strengthens the magnetic field to make the motor spin fast on a lower current
0.02 A flows in 0.1 m of wire in a 5 T magnetic field. What force acts on the wire?
A full circuit is maintained in an electric motor. How is this achieved?
The split ring commutator is connected to a pair of wires
The split ring commutator makes contact with brushes every half turn
The brushes spin and touch the split ring commutator