P7: The Motor Effect

Question 1

What is the motor effect?

Answer 1

When a wire with a current flowing through it is placed in a magnetic field, the magnet and conductor experiences a force.

Question 2

What is the motor effect caused by?

Answer 2

The field made by the current interacts with the magnetic field that the wire is placed inside, causing the force on it.

Question 3

What does the magnitude of the force depend on?

Answer 3

• Current
• Strength of magnets
• Length of wire in magnetic field

Question 4

How do we get the maximum force?

Answer 4

When current flows at right angles to the field.

Question 5

How do we stop the force?

Answer 5

Making the current flow parallel to the field.

Question 6

How is the direction of force reversed?

Answer 6

• Reversing current

- Reversing magnetic field

Question 7

What is Fleming’s left hand rule?

Answer 7

Thumb = Force
Index Finger = Field
Middle Finger = Current
(Force Field Current)

Question 8

What is the formula for magnitude of force? (for currents at 90 degrees to field)

Answer 8

F = BIL
F = force in newtons, N
B = magnetic field strength in tesla, T
I = current in amps, A
L = length of wire in field in metres, m

Question 9

What force acts on current 2A flowing down wire in magnetic field strength 0.01 T if 10cm of wire is in field?

Answer 9

0.002N

10cm = 0.1m
2 x 0.01 x 0.1 = 0.002N

Question 10

What is the symbol for current away going away from you?

Answer 10

x with circle around it. (like back of dart on board)

Question 11

What is the symbol for current away going towards you?

Answer 11

. with circle around it (like sharp end of dart)