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P2 Revision
1
Static Electricity
How are objects Charged?
Friction causes Insulators to become charged
because electrons are transferred.
2
Static Electricity
How do charged objects behave?
Like charges repel unlike charges attract
3
Static Electricity
Why are metals good conductors?
Metals are good conductors because they have
free electrons
4
Electricity
I-V Graph for a resistor?
Current
(I) Amps
Voltage
(V) Volts
5
Electricity
I-V Graph for a bulb?
Current
(I) Amps
Voltage
(V) Volts
6
Electricity
I-V Graph for a diode?
Current
(I) Amps
Voltage
(V) Volts
7
Electricity
What are the advantages of LED’s?
LED’s are more efficient than light bulbs because
they produce less heat
8
Electricity
State Ohms Law?
Ohms Law—The current through a conductor is
proportional to the voltage across it provided that the
temperature stays constant.
9
Electricity
How are ammeters and voltmeters
connected?
Ammeters are connected in series.
Voltmeters are connected in parallel
10
Electricity
What does a thermistor do?
The resistance of a thermistor goes down when
the temperature goes up
11
Electricity
What does an LDR do?
The resistance of an LDR goes down when the
brightness goes up
12
Electricity
What about current and voltage in
parallel circuits?
In a parallel circuit the voltage is the same across each
device but the current splits up—most current will
take the path of least resistance.
13
Electricity
What about current and voltage in
series circuits?
In a series circuit the current is the same
everywhere and the voltages across devices must
add up to the battery voltage
.
14
Mains Electricity
What is ac current?
AC current constantly changes direction. ( Mains)
15
Mains Electricity
What is dc current?
DC flows in one direction. (Battery)
16
Mains Electricity
What is the frequency and voltage of
mains electricity?
The frequency of mains voltage is 50Hz.
The voltage of mains electricity is 230V
17
Mains Electricity
What are the colour of the wires in a plug?
Live—Brown ( fuse in here)
Neutral Blue
Earth Green and Yellow
Cord grip
18
Mains Electricity
Explain how a fuse works?
When a current bigger than the fuse rating
flows through, the fuse gets hot, melts and
cuts off the power. The fuse prevents fires .
Not as good as a circuit breaker which is
quicker & easily reset.
19
Mains Electricity
Explain how the earth wire works?
If a fault develops and the live wire touches the
metal case , a large current flows through the
earth wire, blows the fuse and cuts off the power.
( Not if its Double insulated!)
20
Radioactivity
What is meant by the mass number and
proton number?
Mass number—number of protons and neutron
Atomic number—number of protons
21
Radioactivity
What are the properties of protons
neutrons and electrons?
Proton mass 1 charge +1
Neutron mass 1 charge 0
Electron mass 0 charge –1
22
Radioactivity
Why is an atom neutral?
An atom is neutral because it has the same
number of positive protons and negative electrons
An ion is an atom that has gained or lost electrons.
23
Radioactivity
What are isotopes?
Isotopes are atoms of the same element with the
same number of protons and different numbers
of neutrons.
24
Radioactivity
What causes background radiation?
Natural - Rocks & Cosmic Rays
Man– Made - Nuclear weapons tests and fallout
from nuclear bombs
25
Radioactivity
What are the three types of radiation?
Alpha—helium nucleus ( +2)
Beta—fast moving electron (-1)
Gamma EM wave (o)
Alpha & beta affected by electric and magnetic fields
because they are charged
26
Radioactivity
What is meant by half life?
The half life of an element is the time taken for
half the number of radioactive atoms to decay.
27
Radioactivity
What is nuclear fission & Fusion?
Nuclear fission is the splitting up of large nuclei to
form small nuclei. ( reactors)
Nuclear fusion is the joining together of light
nuclei to form larger nuclei. (Stars)
28
Radioactivity
Can you describe the life of a star?
29
Radioactivity
What is special about a main sequence
star?
In a main sequence star the forces are balanced , it
is fusing hydrogen to produce helium.
30
Radioactivity
Describe how a nuclear power station
works?
Nuclear power station - water heated by reactor,
controlled by boron rods ( absorb neutrons ),
steam drives turbines which drive generator.
31
Radioactivity
Describe a chain reaction?
32
Forces and Motion
What can you work out from this graph?
The gradient of a d-t graph = speed
33
Forces and Motion
What can you work out from this graph?
Area under v-t graph = distance
Gradient of v-t graph = acceleration
34
Forces and Motion
What happens when an object moves
through a fluid?
The faster an object moves through a fluid the
greater is the resistance.
Opening a parachute increases air resistance and
slows you down.
35
Forces and Motion
Describe the fall of a parachutist?
A skydiver accelerates because of her weight ,
acceleration gets less as velocity increases because
air resistance increases, eventually air resistance =
weight and terminal velocity is reached.
36
Forces and Motion
What is meant by thinking distance?
The thinking distance is the distance the car travel
whilst the driver is reacting. It depends on speed,
consumption of alcohol or drugs.
37
Forces and Motion
What is meant by braking distance?
The braking distance is the distance the car travel
from the moment the driver brakes until the car
stops. It depends on the condition of the brakes,
tyres and if the road is wet or icy.
38
Forces and Motion
What is meant by total stopping
distance?
The total stopping distance is sum of the thinking
distance and braking distance.
39
Forces and Motion
What is meant by velocity?
Velocity is speed in a certain direction
40
Forces and Motion
What is meant by the resultant force?
A resultant force is the one force that would have
the same effect as all the other forces combined.
41
Forces and Motion
What is momentum?
Momentum = mass x velocity
It is measured in kgm/s
42
Forces and Motion
What is the law of conservation of
momentum?
The law of conservation of momentum
states that in a closed system the total
momentum before a collision is equal to
the total momentum after a collision.
43
Forces and Motion
What determines the force on a object?
The force on an object
= change in momentum / time of impact
Time of impact is increased in crumple zones, air bags,
crash barriers & soft surfaces to reduce force and injury.
44
Forces and Motion
What is Hookes law ?
Hookes law— the extension of an object
is directly proportional to its load
provided that its elastic limit has not
been reached.
45
Forces and Motion
What is meant by the spring constant?
F=kxe
k is the spring constant
& tells us how much force
Is needed to stretch the spring by 1 m or 1 cm.
46
Forces and Motion
What does elastic mean?
An object is elastic if it returns to its
original shape once the force has been
removed.
47
Forces and Motion
What does work mean?
Work is measured in joules.
Work = force x distance moved in the direction of
the force.
Brakes do work when they change KE to Heat
48
Forces and Motion
What does KE mean?
KE is measured in joules.
KE = ½ x mass x velocity 2
49
Forces and Motion
What does GPE mean?
GPE is measured in joules.
GPE = mass x g x height
50