Magnetic fields

Question 1

What is a magnetic field due to?

Answer 1

Moving charges or permanent magnets

Question 2

What direction does a magnetic field go?

Answer 2

North —> South

Question 3

What are the magnetic field lines for a current-carrying wire?

Answer 3

Concentric circles centred on the wire and perpendicular to it

Question 4

How can you determine the direction of a magnetic field around a current-carrying wire?

Answer 4

Right hand grip rule

1. Using right hand, point the thumb in the direction of the conventional current (+ve to -ve)
2. The direction the fingers wrap around = the direction of the magnetic field

Question 5

What do you use Flemings left hand rule for?

Answer 5

Figuring out the direction of the force experienced by a current-carrying conductor placed perpendicular to the external magnetic field

Question 6

How do you use Flemings left hand rule?

Answer 6

1. Use right hand grip rule to figure out direction of magnetic field.
2. First finger = Direction of external magnetic field
3. Second finger = Direction of conventional current (+ve to -ve)
4. Thumb= Direction of force (motion) of the wire

Question 7

What factors affect the the magnitude of the force experienced by a wire in a n external magnetic field?

Answer 7

F = BILsinø

I = current
L = length of hte wire in the magnetic field
ø = angle between the magnetic field and the direction of the current
Strength of the magnet

Question 8

What is Magnetic flux density and what is it measured in?

Answer 8

The strength of a magnetic field
B/T

Question 9

Define 1T

Answer 9

The magnetic flux density is 1T when a wire carrying a current of 1A placed perpendicular to the magnetic field experiences a force of 1N per metre of its length

Question 10

when is the force at maximum?

Answer 10

When the wire is perpendicular to the field

ø = 90
sinø = 1
B = F/IL

Question 11

when is the force at maximum?

Answer 11

When the wire is perpendicular to the field

ø = 90
sinø = 1
B = F/IL