P5

Question 1

Describe the forces between magnets

Answer 1

North and South Pole
Like poles -> repulsion
Opposite poles -> attraction

Question 2

What is a magnetic field?

Answer 2

Region around a magnet where it has magnetic effects on a magnetic material (force experienced)

Question 3

Describe the forces between a magnet and a magnetic material

Answer 3

A magnetic material experiences a force when in a magnetic field

If the material is un magnetized -> always attracted to magnet

If the material is magnetized -> forms a magnet and acts like one

Question 4

What is induced magnetism?

Answer 4

When iron (or a metal with magnetic properties) it can be magnetized via different methods to turn it into a magnet

Induced magnet -> temporarily magnetic (ex: soft iron)

Permanent magnet -> doesn’t lose magnetism (ex: hard iron/steel)

Question 5

How can a magnetic material be magnetized?

Answer 5

1. Stroking a magnet along the object from one end to the other repeatedly
2. Holding the object in a magnetic field and hitting it
3. Putting the object in a strong magnetic field

Question 6

How can you demagnetize a magnet?

Answer 6

Hitting (outside of a magnetic field) or heating

Question 7

Draw the field lines around a bar magnet

Answer 7

Make sure:
The arrows go from N -> S (convention)
Lines never cross
Lines are closer together when they are closer to the magnet

Question 8

What happens to domains in a magnetic material when it becomes magnetized ?

Answer 8

Un magnetized -> domains unaligned
Magnetized -> domain aligned

Question 9

What are the magnetic properties of soft and hard iron?

Answer 9

Soft iron:
Easily magnetized
Cannot retain magnetism
Good for electromagnets

Steel/hard iron:
Hard to magnetize
Retains magnetism
Used to create permanent magnets

Question 10

What are the properties of permanent and electromagnets?

Answer 10

Permanent:
Permanently magnetized -> cannot be turned on/off
Electrons have intrinsic magnetic field which add up to create one big magnetic field

Electromagnets:
Becomes magnetized when electricity is flowing through it
Charged particles move through a space and INDUCE a magnetic field

Question 11

What is charge measured in?

Answer 11

Coulombs (C)

Question 12

T of F: like charges attract

Answer 12

F: unlike charges attract and like charges repel

Question 13

Describe an experiment that can be done to show the production and detection of electrostatic charge by friction

Answer 13

Inflate balloon -> rub against fabric -> turn on tap -> hold balloon next to water -> water bends towards balloon

A result of the charges of the materials:
Balloon -> negative
Water -> positive particles are attracted to negative balloon

Question 14

How is a material charged?

Answer 14

When 2 insulators are rubbed together -> oppositely charged

Electrons removed from one material (now Pos)
Electrons lost go to the other material (now neg)

To discharge -> touch conductor or earth

Question 15

What is electrostatic induction?

Answer 15

When a charged object is held near an uncharged one -> the opposite charge is induced to the side closest to the charged object

Question 16

What is the equation for electric field strength?

Answer 16

E = electric field strength
F = force (in newtons)
Q = charge (in coulombs)

E = F/Q

Question 17

What is an electric field?

Answer 17

A region in which an electric charge experiences a force

Question 18

What are electrical conductors and insulators ?

Answer 18

Conductors:
Current can flow through
Ex: silver, copper, aluminum, steel

Insulators:
Doesn’t allow flow of charge/current
Ex: plastic, wood, glass, rubber, acetate

Question 19

What is current?

Answer 19

The flow of electrons/charge in a circuit

Convention current goes from Pos -> neg
Reality -> other way/ movement of electrons

Measured in Amps (A)

Question 20

What is potential difference/voltage?

Answer 20

Work done by a unit of charge passing through a component
Must exist for current to flow -> think of its as pushing the current

(in a series circuit) power/pd is used to push, so there will be a difference in energy between the beginning and end of the component

Measured in volts (V)

Question 21

What is emf?

Answer 21

Electromotive force
Sum of all voltage

Work done by a power source in moving a unit of charge -> around the ENTIRE CIRCUIT

Electrical source of energy

Measured in volts (V)

Question 22

What is resistance?

Answer 22

The opposition to a current (measured by how difficult it is to push the current)

Measured on Ohms ( Ω )

Question 23

What is an equation for current? (Using charge)

Answer 23

Current -> rate of flow of charge at a given point

I = current
Q = charge
t = time

I = Q/t

Question 24

Why is metal a good conductor?

Answer 24

Metals -> loose electrons
Current is the flow of these electrons, and since they can move freely and carry charge it makes metal a good conductor

Question 25

What is the use of an ammeter (analogue and digital)?

Answer 25

Measured current
Connected in series

Question 26

What is the use of a voltmeter (analogue and digital)?

Answer 26

Mesures voltage
Connected in parallel

Question 27

What is an equation for current?

Answer 27

R = V (voltage)/ I (current)

A change in voltage or current causes a change in resistance

Question 28

What is a resistor?

Answer 28

A device with a specific resistance

Current-voltage graph -> straight line through the center (gradient +1)

Question 29

What does the current voltage graph of a filament lamp look like like?

Answer 29

Curved -> checks notes

When the line flattens the wire has melted

Question 30

How does heat relate to resistance?

Answer 30

Wire heats -> atoms shake more -> more resistance -> more heat

Question 31

How does length and diameter of the wire affect resistance?

Answer 31

Longer -> electrons collide more with ions -> more resistance

Diameter bigger -> more space for electrons to flow -> less resistance

Question 32

What is electric power measured in?

Answer 32

Watts (W)
Joules/s