Magnetism & Electromagnetism

Question 1

Which directions to does magnetic field lines flow?

Answer 1

North to South

Question 2

What is the law of magnetism?

Answer 2

When two magnets are held close together, there will be an attractive or repulsive force

Question 3

Opposite poles ____

Answer 3

Attract

Question 4

Like poles _____

Answer 4

Repel

Question 5

Why are some materials ‘soft” magnetic materials?

Answer 5

They can easily magnetize and demagnetize

Question 6

What are permanent magnets made of?

Answer 6

Hard magnetic material

Question 7

What are electromagnets made form?

Answer 7

Soft magnetic materials

Question 8

Define magnetic field lines

Answer 8

The region around a magnet where a force acts on another magnet or on a magnetic material

Question 9

What two things do magnetic field line represent?

Answer 9

The strength and direction of magnetic field

Question 10

How is the strength of a magnetic field shown?

Answer 10

By the spacing of the magnetic field lines

Question 11

Where is the magnetic field the strongest

Answer 11

At the poles

Question 12

How is a uniform magnetic field produced

Answer 12

Two opposite poles are held close together

Question 13

Name two characteristics that show a magnetic field is uniform.

Answer 13

Fields lines are equidistant
Field lines are parallel

Question 15

Name two characteristics of a uniform magnetic field.

Answer 15

Same strength and direction and all points

Question 16

Name all four magnetic materials

Answer 16

N - nickel
I - iron
C - cobalt
S - steel

Question 17

Which poles are magnetic fields attracted to?

Answer 17

Both - north and south

Question 18

What are the two types of magnets?

Answer 18

Permanent magnets
Induced magnets

Question 19

When current flows through a wire a _________ ____________ Is produced

Answer 19

Magnetic field

Question 20

What method is used toe work out the direction of a current induced magnetic field?

Answer 20

The right - hand rule
Plotting compass

Question 21

Name two factors that affect magnetic field strength in wire magnets.

Answer 21

Size of current
Distance to long straight conductor

Question 22

The motor effect occurs when: ____

Answer 22

A wire with current flowing through is placed in a magnetic field and experiences a force

Question 23

Why does the motor effect happen?

Answer 23

Due to the two interacting magnetic fields

Question 24

Explain the process happening in a D.C electrical motor?

Answer 24

Horizontal coil of wire in a uniform magnetic field using a split ring commutator

• Current flows through coil producing a magnetic field - leading to that interaction of magnetic fields
• Forced produced in opposite directions on each side of coil
• Once coils has rotates 180 degrees the split ring commutator reconnects with contacts
• Direction of current through wire changes leading to continued rotation as forces stay the same relative to uniform magnetic field

Question 25

Explain the process of a loudspeaker producing sound?

Answer 25

*coil of wire which is wrapped around one pole of the permanent magnet connected to speaker cone* - Alternating current passes through coil - Current is constantly changing directions - Magnetic field of permanent magnet and coil interact - Interacting felid exert a force - constantly changing magnetic field causes force on the coil to constantly change directions - Oscillating coil causes the speaker cone to oscillate

Question 26

In footings left hand rule which finger is what?

Answer 26

Thumb = force Index = permanent magnetic field Middle = flow of current

Question 27

What vectors affect strength of electromagnetic field?

Answer 27

Size of current Number of turns of the coil

Question 28

What is a solenoid?

Answer 28

Wire looped in a coil

Question 29

How does deflecting occur?

Answer 29

When a charged particle passes through a magnetic feild

Question 30

Electromagnetic induction occurs when _____

Answer 30

A voltage issue induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes through it. ‘Cutting the flux’

Question 31

Define potential difference.

Answer 31

A potential difference will be induced in the conductor if there is relative movement between the conductor and the magnetic feild

Question 32

Name three factors affecting the size of the induced potential difference.

Answer 32

- Speed - in which the wire,coil or magnet moves - Number of turns - of the coil - Size - of the coil - strength - of the magnetic feilds

Question 33

Name the factor effecting direction of current in EM induction?

Answer 33

Orientation of the poles of magnet/ reversing the direction in which the wire, coil or magnet is moved

Question 34

Describe the process of generating a.c current using an alternator?

Answer 34

- Coil is forced to spin in a uniform magnetic field - Coil connected to center-reading meter by metal brushes and slip ring - Coil turns in one direction - Coil cuts through the magnetic field lines, alternating pd & current induced

Question 35

What is an alternator?

Answer 35

A type of generator used to produce an alternating current using induction.

Question 36

What is a Dynamo?

Answer 36

a direct current generator

Question 37

Describe the process of producing a d.c current using dynamo.

Answer 37

- As coil is forced to rotate, it cuts through field lines - Split rings changes the connections between coil and brushes every 180, makes sure current leaving is in the same direction - Potential difference does not reverse

Question 38

What is a transformer?

Answer 38

A device used to change the value of an alternating potential difference or current

Question 39

Components of basic transformer?

Answer 39

Primary coil Secondary coil Iron core

Question 40

Why is an iron core used in transformers?

Answer 40

They are easily magnetized and demagnetized

Question 41

Describe the process happening in a transformer.

Answer 41

- Alternating current is provided to P coil - Current changes direction - Iron core is easily magnetized, produces changing magnetic field - Now changing magnetic field in since S coil - Field cuts S coil, induces pd - Changing magnetic field produces alternating pd

Question 42

What are transformers used for?

Answer 42

To change the size of an alternating voltage

Question 43

What is a step-up transformer?

Answer 43

Used to increase the potential difference of a power source MORE turns on the S coil Secondary coil

Question 44

What is a step up transformer?

Answer 44

Used to decrease the pd LESS turns on S coil

Question 45

Why are step-up transformers used in national grid? Where are they placed?

Answer 45

Placed after power station Uses to increase voltage while traveling over large distances High voltage = low current Low current = less heat loss

Question 46

Why are step-down transformers used in the national grid? Where are they used?

Answer 46

For domestic use electricity, voltage must be low. Placed before buildings