The motor effect

Question 1

why is a relay used for?

Answer 1

this is so high voltage circuits can be turned of and on and without sparking and electrocution.

Question 2

how can a relay be used to make high voltage circuits easy to turn off and on?

Answer 2

a relay contains 2 seperate circuits:

1. a low voltage circuit containing an electromagent which is safe to be turned off and on
2. on the high voltage circuit we replace the switch with 2 metal contacts
   * one of the contacts is attached to spring to keep the contacts aprt
   * we also have an iron block

Question 3

how does this set up work

Answer 3

1. current flows through the low voltage circuit, so this induced a magentic field around the electromagnet
2. the magnetic field attracts the iron block
3. this cuases the contacts to close and the swithces on the high voltage circuit

Question 4

how does a doorbell work?

Answer 4

1. the switch is close which causes current to flow
2. a magnetic field is now induced by the electromagent
3. the iron contact is now attracted to the magnetic field
4. when the iron contact moves, the clapper hits the bell
5. this breakes the cicuit at the same time as when the iron conntact moves forward the curcuit breaks there is no current flowing so no magnetic field.
6. iron contact springs back to its original position
7. process is repeated

Question 5

what is the motor effect?

Answer 5

1. when a wire carrying current induces a magnetic field around it
2. if you place this wire at a right angle in magnetic field the 2 fields interact.

3.the wire experiances a force and it is pushed in a direction.

Question 6

how can we calculate the force caused by the motor effect?

which equation??

Answer 6

magentic flux density is the measure of strength of the magnetic field

Question 7

what are the three 3 factors the force depends on?

Answer 7

• length of the conductor
• magentic flux densiry
• current size

Question 8

how to use flemming left hand rule?

Answer 8

1. place your thumb, first finger and second finger at right angles
2. now point your first finger in the direction of the magentic field
3. point your second finger in the direction of the conventional current
4. point your thumb towards the direction of the force

FBI

Question 9

what happens if the conductor is parraleel to the magnetic field?

Answer 9

it will not experinace no force

Question 10

what do the brushes do in an electric motor?

Answer 10

allow electric current to pass onto the split ring

Question 11

how does a electric motor work?

Answer 11

1. current induces a magnetic feild around the wire
2. this interacts with the magnetic field of the magnet
3. this causes the opposing forces on the wire which makes it spin
4. the split ring commutator and brush contacts maintain the electrical current and switch the curret every half turn
5. the momentum keeps it spinning when parallel

Question 12

how does a loudspeaker work?

Answer 12

1. An alternating currentr in the wire induces a magentic material which intercatswith the magnetic feild around the permanent magnet
2. this pushes the cone out and then changes direction and pulls the cone in
3. this causes a pressure chnage inthe air and causes sound waves
4. the alternating current frequency matches the audio

watch video again if not understanding