P5 Electricity and Magnetism

Question 1

What is an electric field?

Answer 1

A region of space in which the effects of
charge can be felt. When another charge
enters the field, both charges interact
and experience a force.

Question 2

What is charging?

Answer 2

The addition or removal of electrons from
a material.

Question 3

What is a conductor?

Answer 3

A conductor is a material which can
conduct electricity; electrons are able to
flow through it. copper, gold

Question 4

What is an insulator?

Answer 4

An object which does not conduct
electricity. Electrons cannot flow through
the material.

Question 5

How is static electricity produced?

Answer 5

When two insulators are rubbed
together, transferring electrons, to form a
positive and a negative charge.

Question 6

What is an electric current?

Answer 6

Current is the rate of flow of charge in an
electric circuit.

Question 7

What is required in order for a
charge/current to flow?

Answer 7

A potential difference
A closed circuit

Question 8

Give an equation linking charge and
current, giving SI units

Answer 8

charge (C) = current (A) x time (s)

Question 9

How is current measured

Answer 9

Using an ammeter, wired in series to the
circuit

Question 10

What is conventional current?

Answer 10

Conventional current (used in circuit
diagrams etc.) represents the flow of
positive charge; it flows in the opposite
direction to the flow of electrons.

Question 11

What is EMF?

Answer 11

Electromotive force (the voltage supplied
by a power source)

Question 12

What are the units of EMF?

Answer 12

Volts, V

Question 13

Define EMF in terms of energy

Answer 13

The energy supplied by the source per
unit charge around the circuit.

Question 14

Define potential difference

Answer 14

The work done per unit charge flowing
between any two points.

Question 15

How is potential difference measured?

Answer 15

Using a voltmeter, wired in parallel.

Question 16

What is 1V equivalent to?

Answer 16

1 Joule per Coulomb

Question 17

Give an equation linking current and
voltage, giving all SI units

Answer 17

p.d. (V) = current (A) x resistance (𝝮)

Question 18

How does resistance affect the current
flowing through a circuit?

Answer 18

The larger the total resistance in the
circuit, the smaller the current will be.

Question 19

How does resistance relate to the length
of a wire?

Answer 19

Resistance increases with length.
R ∝ L

Question 20

How does resistance relate to the cross
sectional area of a wire?

Answer 20

Resistance decreases as cross sectional
area increases (they are inversely
proportional).
R ∝ 1/A

Question 21

How is energy transferred in a circuit?

Answer 21

From the battery/power source to the
circuit components, and dissipated into
the surroundings as heat

Question 22

What factors affect the energy
transferred when charge flows through a
component?

Answer 22

Amount of charge
● The potential difference across the
component

Question 23

Resistance Formula is

Answer 23

R = V I.

Question 24

What is a magnetic field?

Answer 24

A region where magnetic objects
experience a force.

Question 25

Where is a magnetic field strongest?

Answer 25

At the poles of a magnet

Question 26

Magnetic field strength decreases as...

Answer 26

Distance from the magnet increases.

Question 27

Describe the key features of field lines in a magnetic diagram

Answer 27

They have arrows pointing from north to south. ● The lines never touch, cross or overlap.

Question 28

How is the strength of a magnet displayed in a diagram?

Answer 28

By the spacing of the field lines (the closer together they are, the stronger the magnet)

Question 29

What do the arrows on field lines represent

Answer 29

The direction of the force that would be experienced by the north pole of a magnet placed in the field.

Question 30

What is a permanent magnet?

Answer 30

An object which always has poles, and is therefore always magnetic.

Question 31

What is an induced magnet?

Answer 31

A magnetic material which does not have fixed poles. They can be induced to become magnets (giving them poles) by placing them in a magnetic field, but they lose their magnetisation when the field is removed.

Question 32

What is a magnetic material?

Answer 32

A material that is attracted to a magnet and can be magnetised.

Question 33

Give examples of magnetic materials.

Answer 33

Iron, steel, cobalt, nickel etc.

Question 34

Describe how materials are magnetised.

Answer 34

-Stroking them with a magnet -Hammering them in a magnetic field -Placing them in a coil with a direct current through it

Question 35

Describe how materials are demagnetised

Answer 35

-Hammering ● Heating ● Placing in a coil with an AC wire

Question 36

What is a magnetically hard material?

Answer 36

A material which can be permanently magnetised.

Question 37

Give one example of a material that is magnetically hard.

Answer 37

steel

Question 38

What is a magnetically soft material?

Answer 38

A material which is only temporarily magnetised (or does not hold its magnetism very well)

Question 39

Give an example of a magnetically soft material.

Answer 39

Soft iron.

Question 40

Give an example of where electromagnets are more useful than permanent magnets

Answer 40

Magnets used for moving scrap metal; they can be turned off to drop the metal where it needs to be transported to.

Question 41

Describe how magnetic field shapes can be investigated.

Answer 41

Using plotting compasses arranged around a magnet; they will point towards the north pole, showing the direction of field lines.