p7 magnetism and electromagnetism

Question 1

what are the poles on a magnet called

Answer 1

north pole and south pole

Question 2

what will happen if like poles are brought together

Answer 2

the will repel

Question 3

what happens if opposite poles are brought together

Answer 3

they will attract

Question 4

what metals are magnetic

Answer 4

iron, colbalt and nickel

Question 5

what is a permanent magnet

Answer 5

one with its own magnetic field, it cannot be turned on or off

Question 6

what is an induced magnet

Answer 6

a material which only becomes magnetic when placed within a magnetic field

Question 7

what is a magnetic field

Answer 7

the area surrounding a magnet where the force is acting on another magnet or magnetic material

Question 8

what is the motor effect

Answer 8

when a wire carrying a current is exposed to the magnetic field of another magnet, then a force is produced on the wire at a right angle to the direction of the magnetic field produced

Question 9

when is flemings left hand rule used

Answer 9

when a diagram asks you to indicate the direction of the force produced

Question 10

how does an electric motor work

Answer 10

when the wire carrying the current of coiled, the motor effecr acting on it causes the wire to rotate

Question 11

1st step of electric motor workings

Answer 11

as the current flows, the force produced each side of the coil acts in opposite directions, causing the coil to rotate overall

Question 12

2nd step of electric motor workings

Answer 12

when the coil reaches a vertical position, the force is now parallel to the magnetic field line and so would be 0. Causing the motor to stop rotatting

Question 13

3rd step of electric motor workings

Answer 13

to maintain rotation, a split ring commutator is used to supply current to the wire. The dc supply reaches the split ring which maintains the connection while allowing it to rotate freely on the axle.

Question 14

how do headphones work

Answer 14

• an alternating current is supplied through a coil of wire in the loudspeaker
• this produces a magnetic field
  -the electromagnetic field interacts with the magnetic field surrounding the permanent magnet and a force is produced
  -the force produced pushes the cone in the loudspeaker outwards
• the current is reversed, pulling the cone back in
  -the vibrations of the cone creates sound waves
  -these sound waves produced match the electrical signals supplied