Magnetism Flashcards
What is the motor effect? (LS M Ph)
When a conducter (wire) is carrying a current, it experiences a force in a magnetic field.
What is the setup of a Loud Speaker? (LS M Ph)
- a cone which has a coil of wire wrapped around one end
- the wire is connected to an alternating current electrical supply
- a permanent magnet which goes inside the coil of wire
How does a loud speaker work? (LS M Ph)
- as the current passes through the coil, it generates a magnetic field
- the magnetic field of the coil interacts with the magnetic field of the permanent magnet. (these fields either retract or repel echother)
- this produced a resultant force which causes the cone to move.
- when the current switches direction, the direction of the force on the cone reverses.
- this causes the cone to move in and out, generating sound waves
- by changing the frequency of the AC supply, we can change the frequency that the cone vibrates
- if we increase the size of the current, then we increase the amplitude of the vibration
What do we call the two ends of a magnet? (PAIM M Ph)
Poles (north and south poles)
Where are the magnetic forces of a magnet strongest? (PAIM M Ph)
At the poles
What happens when we bring two magnets close to each other? (PAIM M Ph)
They exert a non-contact force on each other. Two like poles repel. Two unlike poles attract each other.
What does a permanent magnet do? (PAIM M Ph)
Produces its own magnetic field. E.g the bar magnets.
When we bring two permanent magnets together then they can attract or repel each other depending on the direction.
What is an induced magnet? (PAIM M Ph)
a material that temporarily becomes magnetic when placed in an external magnetic field.Unlike permanent magnets, which retain their magnetism, induced magnets lose their magnetism when removed from the field.
What happens in terms of magnetism when a current moves through a wire? (TME M Ph)
A magnetic field is produced
When a current passes through a wire it generates a magnetic field, what would happen when we place this in another magnetic field? (TME M Ph)
When a current passes through a wire it generates a magnetic field and then we place that in another magnetic field. The magnetic forces interact with each other and the wire experiences a force.
What is the motor effect? (TME M Ph)
When a current passes through a wire it generates a magnetic field and then we place that in another magnetic field. These interact and the wire experiences a force.
What is the magnetic flux density? (TME M Ph)
A measure of the strength of the magnetic field.
What does the force created by magnetism on a wire depend on? (TME M Ph)
- magnetic flux density
- current
- length of the conductor
How do you determine the direction of the force created by magnetism on a conductor with a current? (TME M Ph)
Fleming’s left hand rule.
How do you do fleming’s left hand rule? (TME M Ph)
Place your thumb, first finger and second finger so they are at right angles
First finger pointing in the direction of the magnetic field. (N to S)
Second finger in the direction of the conventional current (+ to -)
Thumb tells you the direction of the motion/ force
What is the direction of magnetic fields? (TME M Ph)
North to South
What happens in the motor effect when a conductor is parallel to the magnetic field? (TME M Ph)
It will experience no force. Forces only apply when the conductor is at a right angle to the magnetic field.
What happens in a loudspeaker when we increase the frequency of the alternating current supply? (LS M Ph)
A higher frequency produces a higher sound.
What happens in a loudspeaker when we increase the size of the current from alternating current supply? (LS M Ph)
Increase the amplitude of the vibration which increases the volume
