SP8c Magnetic Forces

Question 1

Why can any wire carrying a current experience a force in a magnetic field?

Answer 1

because the current in the wire creates a magnetic field, and this interacts with the field.

Question 2

What kind of force do magnets experience in a field?

Answer 2

an equal and opposite force.

Question 3

When does the greatest force on a wire occur?

Answer 3

when it is at right angles to a field.

Question 4

When is there no force experienced on a wire?

Answer 4

when it is in the same direction as a field.

Question 5

What does Fleming’s left-hand rule show?

Answer 5

the direction of the force on a wire, the magnetic field, and current.

Question 6

What do fingers represent in Fleming’s left-hand rule?

Answer 6

.thumb - force
.index finger - magnetic field
.middle finger - current

Question 7

What is the strength of a magnetic field called?

Answer 7

the magnetic flux density.

Question 8

Whta is magnetic flux density measured in?

Answer 8

newtons per ampere metre or tesla

Question 9

force = ?

Answer 9

magnetic flux density x current x length

Question 10

What is the function of carbon brushes in a electric motor?

Answer 10

they make electrical contacts between the circuit and the motor.

Question 11

What is the function of a split-ring commutator in a electric motor?

Answer 11

changes currents direction every half turn.