Electromagnetism and Magnetism

Question 1

What are the magnetic materials?

Answer 1

Iron, steel, nickel, cobalt

Question 2

What does it mean if the lines are closer together?

Answer 2

The magnetic field will be stronger

Question 3

where is the magnetic field the strongest?

Answer 3

At the poles

Question 4

what do permanent magnets do?

Answer 4

produce their own magnetic field

Question 5

what do induced magnets do?

Answer 5

become a magnet when they are placed in a magnetic field

Question 6

What makes the magnetic field stronger?

Answer 6

larger current
closer to the wire you are
solenoid

Question 7

How can you increase strength of a solenoid?

Answer 7

add an iron core, that will become induced

Question 8

why are electromagnets useful?

Answer 8

you can switch then on and off to creating a varying force

Question 9

What are uses of electromagnets?

Answer 9

in cranes to attract and pick up things made of magnetic material
within other circuits to act as switches

Question 10

what is the motor effect?

Answer 10

a wire is put between magnetic poles, magnetic field around wire interacts with magnetic field its been placed in. The magnet and the conductor exert a force on eachother and the wire begins to move.

Question 11

what happens when the wire runs parallel to the magnetic field?

Answer 11

it will experience no force

Question 12

what does the force acting on a conductor depend on?

Answer 12

magnetic flux density - shows strength
current
length of conductor in magnetic field

Question 13

what does the split ring commutator do?

Answer 13

swaps the contacts every half turn to keep the motor rotating in same direction

Question 14

How can the direction of motor be reversed?

Answer 14

reversing the current or reversing the field (swapping magnetic poles over)

Question 15

How do loud speakers and headphones work?

Answer 15

alternating current sent through the coil of wire
coile surrounds one pole of perm magnet
surrounded by other pole so current causes force on coil
current reversed
force acts in opposite direction
cone moves in opposite direction
variations of current make cone vibrate to cause pressure then sound waves

Question 16

what is the generator effect?

Answer 16

induction of potential difference in a wire which is moving relative to magnetic field, or change in magnetic field

Question 17

How can you create a potential difference and current in conductor for the generator effect?

Answer 17

moving a magnet in a coil of wire or moving the wire in a magnetic field.

Question 18

what does a change in magnetic field do?

Answer 18

induces a current in a wire

Question 19

Why does the magnetic field created in an induced current acts against the change?

Answer 19

to return things to the way they were, the induced current always opposes the change that made it

Question 20

How do you increased induced potential difference?

Answer 20

increase speed of movement, cutting more magnetic field lines
increase the strength of the magnetic field

Question 21

How do generators produce an alternating potential difference?

Answer 21

they have slip rings and brushes so the contacts dont swap every half turn

Question 22

what do dynamos do?

Answer 22

split-ring commutators to swap connection every half turn to keep current flowing in same direction

Question 23

How do microphones work?

Answer 23

sound waves hit a flexible diaphrgam attached to a coil of wire wrapped around a magnet
coil moves in magnetic field
generates current
movement of coil depends on property of sound waves

Question 24

what do transformers look like?

Answer 24

they have 2 coils of wire, primary and secondary, joined with an iron core.

Question 25

what happens if the second coil of a transformer is a complete circuit?

Answer 25

causes a current to be induced