P2 Revision 1

Friction causes Insulators to become charged because electrons are transferred. Static Electricity How are objects Charged? 2

Like charges repel unlike charges attract Static Electricity How do charged objects behave? 3

Metals are good conductors because they have free electrons Static Electricity Why are metals good conductors? 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

LED’s are more efficient than light bulbs because they produce less heat Electricity What are the advantages of LED’s? 8

Ohms Law—The current through a conductor is proportional to the voltage across it provided that the temperature stays constant. Electricity State Ohms Law? 9

Ammeters are connected in series. Voltmeters are connected in parallel Electricity How are ammeters and voltmeters connected? 10

The resistance of a thermistor goes down when the temperature goes up Electricity What does a thermistor do? 11

The resistance of an LDR goes down when the brightness goes up Electricity What does an LDR do? 12

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. Electricity What about current and voltage in parallel circuits? 13

In a series circuit the current is the same everywhere and the voltages across devices must add up to the battery voltage. Electricity What about current and voltage in series circuits? 14

AC current constantly changes direction. ( Mains) Mains Electricity What is ac current? 15

DC flows in one direction. (Battery) Mains Electricity What is dc current? 16

The frequency of mains voltage is 50Hz. The voltage of mains electricity is 230V Mains Electricity What is the frequency and voltage of mains electricity? 17

Live—Brown ( fuse in here) Neutral Blue Earth Green and Yellow Cord grip Mains Electricity What are the colour of the wires in a plug? 18

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. Mains Electricity Explain how a fuse works? 19

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!) Mains Electricity Explain how the earth wire works? 20

Mass number—number of protons and neutron Atomic number—number of protons Radioactivity What is meant by the mass number and proton number? 21

Proton mass 1 charge +1 Neutron mass 1 charge 0 Electron mass 0 charge –1 Radioactivity What are the properties of protons neutrons and electrons? 22

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. Radioactivity Why is an atom neutral? 23

Isotopes are atoms of the same element with the same number of protons and different numbers of neutrons. Radioactivity What are isotopes? 24

Natural - Rocks & Cosmic Rays Man– Made - Nuclear weapons tests and fallout from nuclear bombs Radioactivity What causes background radiation? 25

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 Radioactivity What are the three types of radiation? 26

The half life of an element is the time taken for half the number of radioactive atoms to decay. Radioactivity What is meant by half life? 27

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) Radioactivity What is nuclear fission & Fusion? 28

Radioactivity Can you describe the life of a star? 29

In a main sequence star the forces are balanced, it is fusing hydrogen to produce helium. Radioactivity What is special about a main sequence star? 30

Nuclear power station - water heated by reactor, controlled by boron rods ( absorb neutrons ), steam drives turbines which drive generator. Radioactivity Describe how a nuclear power station works? 31

Radioactivity Describe a chain reaction? 32

The gradient of a d-t graph = speed Forces and Motion What can you work out from this graph? 33

Area under v-t graph = distance Gradient of v-t graph = acceleration Forces and Motion What can you work out from this graph? 34

The faster an object moves through a fluid the greater is the resistance. Opening a parachute increases air resistance and slows you down. Forces and Motion What happens when an object moves through a fluid? 35

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. Forces and Motion Describe the fall of a parachutist? 36

The thinking distance is the distance the car travel whilst the driver is reacting. It depends on speed, consumption of alcohol or drugs. Forces and Motion What is meant by thinking distance? 37

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. Forces and Motion What is meant by braking distance? 38

The total stopping distance is sum of the thinking distance and braking distance. Forces and Motion What is meant by total stopping distance? 39

Velocity is speed in a certain direction Forces and Motion What is meant by velocity? 40

A resultant force is the one force that would have the same effect as all the other forces combined. Forces and Motion What is meant by the resultant force? 41

Momentum = mass x velocity It is measured in kgm/s Forces and Motion What is momentum? 42

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. Forces and Motion What is the law of conservation of momentum? 43

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. Forces and Motion What determines the force on a object? 44

Hookes law— the extension of an object is directly proportional to its load provided that its elastic limit has not been reached. Forces and Motion What is Hookes law ? 45

F = k x e k is the spring constant & tells us how much force Is needed to stretch the spring by 1 m or 1 cm. Forces and Motion What is meant by the spring constant? 46

An object is elastic if it returns to its original shape once the force has been removed. Forces and Motion What does elastic mean? 47

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 Forces and Motion What does work mean? 48

KE is measured in joules. KE = ½ x mass x velocity 2 Forces and Motion What does KE mean? 49

GPE is measured in joules. GPE = mass x g x height Forces and Motion What does GPE mean? 50