Topic 12

Question 1

describe attraction and repulsion of magnetic poles

Answer 1

unlike magnetic poles attract and like magnet poles repel

Question 2

describe permanent magnets

Answer 2

permanent magnets produce their own magnetic field all the time

Question 3

describe induced magnets

Answer 3

induced magnets only produce a magnetic field while they’re in another magnetic field

Question 4

What does the strength of the field depend on

Answer 4

The size of current and distance from long straight conductor

Question 5

A current carrying conductor placed near a magnet

Answer 5

Experiences a force and an equal and opposite force acts on magnet

Question 6

Define a solenoid

Answer 6

A long coil of wire

Question 7

Describe field lines inside the solenoid

Answer 7

Lots of field lines pointing in same direction. Magnetic field strong and almost uniform

Question 8

Describe field lines outside coil

Answer 8

Overlapping field lines cancel each other out, so field is weak apart from at ends of solenoid

Question 9

Equation to find force acting on conductor

Answer 9

F= BIl
Force acting on conductor at right angles to magnetic field carrying current (N)= magnetic flux density (T or N/A m)
X current (A) x length (m)

Question 10

Explain how force on conductor in magnetic field used to cause rotation in electric motors

Answer 10

Forces act in opposite directions on each side, so coil rotates. Split-ring commutator swaps contacts every half turn to keep motor rotating in same direction