# P2 AQA

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define a force
pushes and pulls (measured in Newtons)
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What is thinking distance?
the distance travelled during the drivers reaction time
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What is stopping distance?
the distance travelled while under the breaking force
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How is terminal velocity reached?
As acceleration increases, so does air resistance and friction, terminal velocity (top speed = no more acceleration) happens when the rate of acceleration=rate of increasing resistive force
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What is gravitational potential energy?
Energy an object has due to its position in the gravitational field
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What is momentum?
tendency of an object to continue int he direction it is going
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How do seat belts and airbags make cars safer?
seat belts stretch in a collision to increase the time it takes for your body's momentum to reach zero = less force upon your body (airbags do the same, and provide a soft cushion)
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what is an elastic collision?
momentum is conserved, no energy lost to surroundings
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what is an inelastic collision?
not all momentum is conserved, some energy lost to surroundings
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What happens in a thermistor?
As temp increases, resistance decreases
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What is resistance?
measure of how difficult it is for a current to flow through a component with a particular P.D
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In a resistor with a constant increasing current, p.d increases at ....
a constant rate
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In a filament lamp with a constantly increasing current, p.d increases ....
in an S shape ( not at a constant rate)
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Why don't current and potential difference in a filament bulb increase proportionally?
The ions in the filament vibrate more, making it harder for electrons to flow
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In a diode with a constantly increasing current, p.d increases ....
in one direction only (current can only flow one way)
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When do electrostatic shocks occur?
When a charged object has contact with an 'earthed' object ( as the electrons jump from the charged object to the earthed one)
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Define resistance
How difficult it is for electrons to move through a component/ the circuit and transfer charge
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What is the rule for resistance in a series?
Riot = R1 + R2 + R3....
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What is the rule for resistance in a parallel?
1/Rtot = 1/R1 + 1/R2 ...
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What type of wire (long, short , thin, thick) experiences the most resistance?
long, thin
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What causes resistance?
the moving electrons collide with ions in the metal
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What is the rule for current in a series?
Current is the same everywhere in the circuit
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What is the rule for current in a parallel?
Current is split between components ( 'branches' ) Itot=I1 + I2 + I3 ....
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Define Potential difference
Work done for 1 column to pass between 2 points in a circuit
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What is the rule for P.D in a series?
Vtot = V1 + V2 + V3 ...
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What is the rule for P.D in a parallel?
P.D is the same everywhere in the circuit
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What is A.C? Why do we use it in the national grid?
alternating current - electrons constantly flowing in different direction, transformers only work using A.C
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What is D.C?
Direct Current, electrons only flow in one direction
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What type of energy source provides A.C?
generators
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What type of energy source provides D.C?
cells/ batteries
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Which 3 wires are in a 3 pin plug?
live, earth, neutral
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What does the live wire do?
supplies the electricity, always carries a current
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What colour is the live wire?
Brown
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Which direction does the live wire go?
to the right , bRown
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What does the earth wire do?
(for metal cased appliances) creates a safe route for current to flow if current is too high, or live wire comes loose (allows electricity to complete the circuit without flowing through the components)
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What colour is the earth wire?
green and brown
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Which direction does the earth wire go?
up
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What does the neutral wire do?
only carries a current when the appliance is switched on, it completes the circuit
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What colour is the neutral wire?
Blue
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Which direction does the neutral wire go?
Left, bLue
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What is the useful rhyme to remember the colours of the wires?
Live Brown bear sits on the Green and Yellow Earth under the Neutral Blue sky
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Why would an appliance be doubly insulated?
thick plastic stops charge being transferred to user of device if live wire comes loose (no earth wire needed)
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What is a fuse?
A thin wire that melts if current gets too high, breaking the circuit
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How do RCCBs work?
they detect a difference in current between the live and neutral wire, and break the circuit if it is too big
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What are the advantages of RCCBs over fuses
they don't have to be replaced, they are faster, they use less energy to break the circuit
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Which type of atoms emit radiation?
arms with unstable nuclei (as they have too many or too few electrons)
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alpha particles have 2 protons and 2 neutrons
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Beta particles are high energy electrons emitted from the nucleus of an atom after a neutron has split into a proton and electron
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Electromagnetic waves
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Which type of radiation is the most ionising ( damaging to cells )
Alpha, then Beta, then Gamma
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Which type of radiation travels the furthest in air?
Gamma (very far), then Beta (about 20 cm), then Alpha (few cm)
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What is alpha radiation absorbed (stopped) by?
paper, skin
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What is beta radiation absorbed (stopped) by?
thin aluminium sheet
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What is gamma radiation absorbed (stopped) by?
thin concrete wall, or thick lead wall
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Which types of radiation are deflected by magnetic and electric fields?
Alpha - has a large mass (not deflected strongly) is attracted to - plate, Beta (small mass, strongly defected) is attracted to + plate
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What was the plum pudding model?
Ernst Rutherfords atom model, which had negative electrons floating in a + jelly
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Describe nuclear fission
a neutron is fired at an unstable nucleus, causing the nucleus to split into 2 and release energy and neutrons
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Describe nuclear fusion
(very high temp needed, so only happens in stars) 2 or more nuclei join to form a larger nucleus and a neutron (releases loads of energy)
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What is CMBR
microwaves coming from every direction (can only be explained by the big bang)
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Describe the lifecycle of a small star
nebula - protostar - main sequence - (expands) red giant - (cools and condenses) White dwarf - (cools and condenses more) Black dwarf
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Describe the lifecycle of a large star
nebula - protostar - main sequence - (expands) super red giant-(rapidly cools and shrinks, then explodes) Supernova - neutron star - (if star big enough) Black hole
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How are chemical elements smaller than iron formed?
In nuclear fusion in stars (of helium and larger atoms when Hydrogen is running out)
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How are chemical elements larger than iron formed?
In supernova explosions
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What are some issues surrounding generating electricity from nuclear energy?
expensive and dangerous to decommission, radioactive (can cause cancer for workers/ people living nearby), non renewable
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## Other cards in this set

### Card 2

#### Front

What is thinking distance?

#### Back

the distance travelled during the drivers reaction time

### Card 3

#### Front

What is stopping distance?

### Card 4

#### Front

How is terminal velocity reached?

### Card 5

#### Front

What is gravitational potential energy?