ELECTROMAGNETISM

Question 1

what is the right hand thumb rule and what is it used for?

Answer 1

using your right hand you point you thumb up in the direction of current and curl your fingers, the direction of your fingers is the direction of magnetic field

used to work out magnetic field direction

Question 2

what happens when current flows through a wire?

Answer 2

a magnetic field is created around the wire, which is made up of concentric circles perpendicular to the wire

Question 3

what affects the strength of the magnetic field of a wire?

Answer 3

the amount of current (larger=stinger)

proximity to the wire (closer=stronger)

Question 4

what is a solenoid?

Answer 4

a coil of wire

Question 5

what happens if you wrap the wire into a coil called a solenoid?

Answer 5

the strength of the magnetic field increases

Question 6

why does the strength of a magnetic field increase when it’s coiled up into a solenoid?

Answer 6

because the field lines around the loop line up with each other

which results in lots of field lines pointing in the same direction, and being very close together
causing it to be strong

Question 7

how can you increase the field strength of a solenoid even more?

Answer 7

by adding an iron core to the centre of the solenoid

this iron core becomes an induced magnet when current flows into it

Question 8

why is iron used as the core of an electromagnet?

Answer 8

because it is magnetically soft

Question 9

what is an electromagnet?

Answer 9

a solenoid with an iron core with a magnetic field that can be switched on and off with electric current

Question 10

describe two uses of electromagnets (4 marks)

Answer 10

used in cranes to attract and pick up things made of magnetic material such as iron and steel

this is commonly used in scrap yards

used as a relay switch

when the switch in one circuit is closed it turns on an electromagnet that pulls a piece of iron onto a rocker

the rocker then pivots and closes the contacts causing the secondary circuit to turn on