Topic 13

Question 1

what affetcs size of force produced

Answer 1

• higher current
• length of wire
• magetic field strength

Question 2

when is the force greatest

Answer 2

when the wire is at right angles to the magnetic field

Question 3

force is zero when

Answer 3

the wire is in the same direction as the magnetic field

Question 4

motors

motors

Answer 4

when the current flows through the magnet it has a force going up and when the current flows back through the magnet it has a force going down casuing it to rotate
the direction of the force is opposite on each side of the coil

Question 5

how to change direction of motor

Answer 5

• switch magnets
• reverse current

Question 6

split ring commutator

Answer 6

metal ring is split so that every half turn the current in the coil changes direction this ensures that the force on the coil always turns it in the same direction

Question 7

carbon brushes

Answer 7

• connects cuircuit to the motor they loose contact with the split rings as the coil spins

Question 8

when the magnet is moved ralative to the wire

Answer 8

a current flows changing the direction on the current
this is because the changing magnetic field induces a potential difference in the wire this can also be done by moving a wire in a magnetic field

Question 9

realtive motion

Answer 9

the magnetic field must cut across the wire so there needs to be reltive motion between them, s changing magnetic field
the induced potential difference in the wire casues a current to flow which then produces a magentic current field across the wire

Question 10

idk

Answer 10

when the magnet is moved relative ti the wire a current flows
this is ben=cause the changing magnetic field induces a potential difference in the wire
the magnetic field mst cut across the wire
when a current flows a megnetic field is produced around the wire which is opposite diresction to the origial magnatic field
revisng the direction recuses the direction of the induced potential difference
the size of the induced potential difference depends on the strength of the magentic field snd the speed at which the magnetic field changes ad number of turns the coil of wire takes

Question 11

generators

Answer 11

coil of wire that can be rotaed inside a magentic field
can be connected to slip rings tht are in contact with carbon brushes

some use a rotaing electromagnet

Question 12

alternator

Answer 12

• prodcing AC
• carbon brushes connect the moving coil to an external cuircuit
• ends if teh coil are connected to slip rings

Question 13

dynamo

Answer 13

produces DC
- connections switch every hald turn
- ends of the coil are connected to a commutator
- carbon bruses connect the moving coil to an external cuircuit
- carbon brshes connect the moving coil to an electrical cuircuit

Question 14

microphones

Answer 14

1. sound waves cause pressure vibtarions in the air
2. pressure variations in the air make the diophram move
   3.diaphram makes a coil move backwards and forwards near a permenant magnet
   4.movment of the coil near the magnet induecs a varying current in the coil pf wire
   5.the current in the coil can be recorded or sent to loudspeakers