Section 22&23

Question 1

Magnetics and magnetic fields

Answer 1

All Magnets produce magnetic fields – all magnets have a north and south pole – lines go from north to south
Two poles that are the same will repel
The closer together the lines, the stronger the fields are
Magnetic fields cause forces between magnets – can either be attractive or repulsive– Placing North and South near each other creates a uniform field( if asked to draw uf, draw at least 3 field lines parallel and same distance apart)

Question 2

Permanent and induced magnets

Answer 2

Induced( temporary) - only produce a magnetic field while in another magnetic field- if you put any magnet in another magnetic field it becomes induced
Permanent - produce their own magnetic field all the time
3 main magnetic elements are iron, nickel, colbalt
Uses- fridge doors, doorbells, cranes

Question 3

Electromagnetism and motor effect

Answer 3

A moving Charge creates a magnetic field – The field is made up of concentric circles perpendicular to the wire -changing direction of current changes direction of magnetic field– Use the right-hand thumb rule to work out direction , The larger the current or closer to the wire you are the stronger the field is

Motor affect – a current in a magnetic field experiences a force – to experience full force, angle must be at 90°– Use Fleming’s left-hand rule to find direction (2nd finger = current, thumb = direction of force, first finger = magnetic field)

Question 4

Solenoids and electromagnetic induction

Answer 4

A solenoid is a long coil of wire – inside the solenoid you get lots of field lines pointing in same direction so magnetic field is strong– Outside the coil overlapping field lines cancel each other out so field is weak
A solenoid is an electromagnet

Electromagnetic induction – the induction of the potential difference in a wire which is experiencing the change in magnetic field

Question 5

Transformers

Answer 5

Transformers use electromagnetic induction to make transferring electricity more efficient
Use induction to change the size of potential difference of an alternating-current
They all have two coils of wire, primary and secondary joined with an iron core

Question 6

Transformers in National Grid

Answer 6

Transformers in National Grid produce high potential difference and low current – transmits electricity at high-power – step up transformer used to boost potential difference and keep current low then use stepdown transformers to usable level

Question 7

Step up and stepdown transformers

Answer 7

Step up transformers – they have more turns on the secondary coil than primary coil – step potential difference up

Step down transformers – more turns on primary coil than secondary coil – step potential difference down

Question 8

Density

Answer 8

Measure of the compactness

Question 9

Kinetic theory and states of matter

Answer 9

Gas to liquid = condensing
Liquid to gas = evaporating
Liquid to solid = freezing
Solid to liquid = melting
Solid to gas = subliming
Kinetic theory is a way of explaining matter
Density of a substance varies with state but mass doesn’t

Question 10

Specific heat capacity

Answer 10

Eating a substance increases energy in its thermal energy store (sometimes referred to as internal energy)
Specific heat capacity relates temperature and energy

Question 11

Specific latent heat

Answer 11

Specific latent heat is the energy needed to change state
You need to put in energy to break intermolecular bonds – shown when you melt ice with Bunsen burner (every 20 seconds record the temp)

Question 12

Particle motion in gas

Answer 12

Colliding gas particles creates pressure– More particles in volume, more often they collide, higher the pressure
Increasing the temperature increases the pressure – more energy so collide more
Absolute 0 = 0 Kelvin = – 273°

Question 13

Forces and elasticity

Answer 13

Object has been elastically distorted if it can go back to its original shape – inelastically distorted if it doesn’t

Question 14

Investigating Elaasticity

Answer 14

Faucet extension relationship in a spring practical – can calculate work done for linear relationships

Question 15

Magnets and Magnetic field practical

Answer 15

Plotting compasses show direction of magnetic fields

1. put magnets on paper, draw round it
2. Put compass on paper – needle points in direction of field line – mark it
3. move compass so tail end of needle is where tip of the needle was
4. repeat and join up