6 Electric motors and electromagnetic induction Flashcards
What happens when a charged particle moves through a magnetic field?
It experiences a force.
Under what conditions does a charged particle experience a force?
As long as the charged particles motion is not parallel to the field.
What is an electric current made out of?
Electrons.
How can we demonstrate this effect?
By passing electrons (electric current) along a wire that is placed in a magnetic field. When the switch is closed and electrons flow, the wire will try to move upwards.
Why does the wire try to move upwards?
Because if the wire is placed between the two poles of the magnet, the two fields overlap. Pushing the wire up due to the strong field created at the bottom part of the wire.
How can we explain the motor effect in relation to the different fields and their strengths?
Below the wire, the fields are in the same direction and so reinforce each other, a strong magnetic field is produced here. However, above the wire, the fields are in opposite directions so weaker field is produced here.
What does the wire ‘feel’ due to these different strengths?
Because the fields are different strengths, the wire ‘feels’ a force - that is, in this case, upwards, the overlapping of the two magnetic fields has produced motion. This is called the motor effect.
How do we increase the force prroduced?
- By increasing the magnetic field.
- By increasing the current.
What happens if we change the direction of the current or the magnets field?
A different overlapping pattern is created and we will see the wire move in the opposite direction.
How can we predict the direction of the force or movement of the wire?
Using Fleming’s left-hand rule.
What does the thumb represent?
Motion. So the thumb gives direction of motion or force.
What does the pointer finger represent?
Field. So the pointer finger gives direction of field (N to S).
What does the middle finger represent?
Current. So the middle finger gives direction of current in wire.
What does the moving coil loudspeaker do?
It uses the motor effect to transfer electrical energy into sound energy.
What are the steps that the moving coil loudspeaker takes in order to convert this electrical energy into sound energy?
1) Electric currents from a source, such as a radio, pass through the coils of a speaker.
2) These currents, which represent sounds, are always changing in size and direction, like vibrating sound waves.
3) The fields of the coil and the permanent magnets are therefore creating magnetic field patters which are also always changing in strength and direction.
4) These fields in turn apply rapidly changing forces to the wires of the coil, which cause the speaker cone to vibrate.
5) These vibrations create the sound waves we hear.
What is a picture representing a loudspeaker transferring electrical energy to sound energy?
What is one of the most important uses of the motor effect?
The electric motor.
What is an image that shows an electric motor?
How can we explain how an electric motor uses the motor effect?
- When there is a current in the loop of wire, one side of it will experience a force pushing it upwards. The other side will feel a force pushing it downwards, so the loop will begin to rotate.
- As the loop reaches the vertical position, its momentum takes it past the vertical. If the rotation is to continue the forces on the wires must now be reversed so that the wire at the top is now pushed down and the bottom one is pushed up.
- This can be done easily by sing a split ring to connect the loop of wire to the electrical supply. Now each time the loop of wire passes the vertical position, the connections change, the direction of the current charges, and the forces on the different sides of the loop change direction. The loop will rotate continuously.
How can we increase the rate at which the motor turns?
- Increase the number of turns or loops of wire, making a coil.
- Increase the strength of the magnetic field.
- Increase the current in the loop of wire.
How do motors produce movement?
Through electricity.
What machines use motion to produce electricity?
Generators and alternators and they use a process called electromagnetic induction.
What happens if we move a wire across a magnetic field at right angles?
A voltage is induced or generated in the wire.
What happens if the wire is part of a complete circuit?
There is a current.
