4.7.2.1 Electromagnetism

Question 1

What happens when a current flows through a wire?

Answer 1

when a current flows through conducting wire a magnetic field is produced around the wire

Question 2

What does the strength of the magnetic field depend on in a wire?

Answer 2

• the strength of the magnetic field depends on the current through the wire
• distance from the wire
• shaping a wire to form a solenoid (coiled) increases the strength of the magnetic field created by a current through a wire - the magnetic field inside a solenoid is strong and uniform
• adding an iron core increases the strength of the magnetic field of a solenoid

Question 3

How do you increase the strength of a magnetic field in a solenoid?

Answer 3

• higher current - increases strength of magnetic field
• increase number of turns of the coil so strength fo magnetic field increases
• place piece of iron in solenoid - iron core

Question 4

What happens to the magnetic field if you change the direction of the current?

Answer 4

if the direction of the current is changed then the direction of the magnetic field will change as well

Question 5

How do you find the direction of the current in a wire?

Answer 5

• right hand grip rule

Question 6

How do you find direction of magnetic field in solenoid?

Answer 6

• place fist of right hand so fingers curl in same direction as conventional current
• thumb will point in direction of N pole

Question 7

What does the magnetic field around a solenoid have?

Answer 7

the magnetic field around a solenoid has a similar shape to that of a bar magnet

Question 8

Electromagnet:

Answer 8

a solenoid with an iron core

Question 9

Why are electromagnets useful?

Answer 9

• can change strength of magnetic field by changing the current
• can turn an electromagnet on or off

Question 10

How do you make an electromagnet?

Answer 10

• power pack
• wire into a coil - solenoid
• magnetic material in coil
• paperclips to test electromagnet
• crocodile clips
• if you remove magnetic material the coil will still be an electromagnet - the iron core just strengthens the electromagnet
• current flowing through the wire creates the magnetic field - anything with current flowing through it has a magnetic field

Question 11

How can you test that there is a magnetic field around a wire?

Answer 11

• when a current flows through a conducting wire - magnetic field around the wire
• use compass to prove there’s a magnetic field around a wire
• when current is turned off, then the compass needle lines up with the Earth’s magnetic field
• if you turn the current on again then the compass needle deflects - this proves that there is a magnetic field around the wie