SP8d Electromagnetic Induction

Question 1

When does electromagnetic induction occur?

Answer 1

when a wire is moved in a magnetic field - a current is produced if there is a complete circuit.

Question 2

What is the size of the induced potential difference determined by? (4)

Answer 2

.the speed at which the wire, coil or magnet is moved
.the number of turns on the coils of wire
.the size of the coils
.the strength of the magnetic field

Question 3

What is the direction of the induced potential difference determind by?

Answer 3

.the orientation of the poles of the magnet

Question 4

Do alternators have alternating or direct current?

Answer 4

alternating.

Question 5

Do dynamos have alternating or direct current?

Answer 5

direct.

Question 6

What is the difference between alternators and dynamos? (where are the ends of their coils connected)

Answer 6

.alternator - ends of the coil connected to slip rings
.dynamo - ends of coil are connected to a commutator

Question 7

What do alternators and dynamo both have?

Answer 7

carbon brushes connecting the moving coil to an external circuit.

Question 8

What does a split-ring commutator do in a dynamo?

Answer 8

it swaps the connections every half turn so the current in the circuit flows in the same direction.

Question 9

Why is it harder to turn the coil of an alternator or dynamo faster?

Answer 9

if the coil is turned faster the induced current is greater which means a stronger magnetic field around the coil that opposes the original movement.

Question 10

How do microphones work in terms of changing pressure variation into variations in electric currents? (5)

Answer 10

1.sound waves cause pressure variation in air
2.pressure variations in air make a diaphragm move
3.the diaphragm makes a coil move backwards and forwards relative to a permanent magnet
4.the relative movement of the coil and magnet induces an ac in the coil of wire
5.the current in coil can be recorded or sent to loudspeakers

Question 11

How do loudspeakers change variation in current to variations in air pressure?

Answer 11

1.an ac flows through a coil creating a magnetic field
2.the magnetic field of coil interacts with the magnetic field of pernament magnet
3.interacting fields exert force on coil causing it to move forwards and backwards
4.the moving coil is connected to the diaphragm which causes the diaphragm to move
5.as the diaphragm moves it causes pressure variations in the air
6.pressure variations in the air cause sound waves