CP12/13 -Magnetism And Electromagnetic Induction

Question 1

What is a permanent magnet?

Answer 1

A magnetic material that constantly produces its own magnetic field.

Question 2

What is an induced magnet?

Answer 2

A material that becomes magnetic when placed in a magnetic field
It is temporary

Question 3

What sides attract and repel?

Answer 3

Opposites attract
Same sides repel

Question 4

How can you use a plotting compass to draw a magnetic field?

Answer 4

Place the compass near the magnet on a piece of paper
Mark the direction the compass needle points
Move the compass around repeatedly marking
Join the points to show the field lines

Question 5

At which pole does the magnetic field always flow?

Answer 5

Into South
Out North

Question 6

What is a magnetic field?

Answer 6

The area surrounding a magnet that can exert force on other magnetic materials.

Question 7

How does a compass work?

Answer 7

The needle is a small magnet
The Earth creates a giant magnetic field
The magnet is attracted to the North Pole of the Earth

Question 8

Name some magnetic materials that are attracted by magnets:

Answer 8

Nickel
Iron
Steel
Cobalt

Question 9

What are some key features of magnetic fields?

Answer 9

The field lines never cross each other
The closer the lines the stronger the magnetic field
The arrows show the direction of the force exerted

Question 10

Explain the magnetic field produced when a current flows in a wire?

Answer 10

A circular magnetic field around the wire
Magnetic field strength is stronger closer to the wire

Question 11

What can you use the Right Hand Rule to find?

Answer 11

Direction of the current
Direction of the magnetic field

Question 12

What is a solenoid?

Answer 12

A coil of wire which can carry an electric current to create a magnetic field

Question 13

Describe the magnetic field lines of a solenoid?

Answer 13

The field lines inside the solenoid are uniform and strong
The further away you get from the solenoid the weaker the magnetic field

Question 14

What is an electromagnet?

Answer 14

A coil of wire with a current flowing through it

Question 15

How can you increase the strength of an electromagnet?

Answer 15

By placing an iron core inside the coil, which becomes a temporary magnet

Question 16

What is the motor effect?

Answer 16

The effect where a force is exerted on a wire carrying a current in a magnetic field

Question 17

Explain the motor effect:

Answer 17

The current in a wire creates a magnetic field around the wire
This magnetic field interacts with the magnetic field between two magnets
The force is greatest when the wire is at right angles to the magnets

Question 18

Explain Flemings Left Hand Rule:

Answer 18

Your thumb is the direction force is exerted
Your index finger is the direction of the magnetic field
Your middle finger is the direction of the current

Question 19

What is electromagnetic induction?

Answer 19

The production of a potential difference when a conductor is moved through a magnetic field
If the conductor is part of an electric circuit an induced current will flow

Question 20

What is the generator effect?

Answer 20

When motion between a conductor and magnetic field creates electricity

Question 21

What are two ways electromagnetic induction can occur?

Answer 21

A coil of wire is moved into a magnetic field
A magnet is moved into a coil of wire

Question 22

How do you increase the potential difference in electromagnetic induction?

Answer 22

Increase the speed of the movement
Increase the magnetic field strength
Increase number of turns in the coil

Question 23

How do you increase magnetic field strength?

Answer 23

Increase number of turns in a coil
Increase the current
Add an iron core to a solenoid

Question 24

What is a transformer?

Answer 24

An electrical device that increases or decreases the potential difference of an alternating current

Question 25

How does a transformer work?

Answer 25

A primary voltage drive an alternating current through the primary coil
The primary coils current produces a magnetic field which changes as the current changes
The iron core increases the strength of the magnetic field
The magnetic field passes through the secondary coil
The changing magnetic field induces a changing potential difference in the secondary coil
The induced potential difference produces an alternating current

Question 26

What does a step-up transformer do?

Answer 26

Increase the voltage
Decreases the current

Question 27

What does a step-down transformer do?

Answer 27

Decreases the voltage
Increases the current

Question 28

Why does the national grid use transformers?

Answer 28

The higher the current, the more the wire heats up because the more heat energy being transferred to the surroundings
To reduce energy loss step-up transformers increase the voltage and decrease the current
But high voltage is dangerous so step-down transformers decrease the voltage and increase the current before the electricity gets to homes