Physics Unit 2

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  • Created by: jenni2906
  • Created on: 16-05-15 11:07
What causes something to become electrically charged?
Friction between objects, causes electron transfer.
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Why does hair stand on end when someone is electrically charged?
All the charges are the same because the hairs are repelling.
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Why does a child not become electrically charged when sliding on metal?
Charge would pass through the metal.
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What star becomes a black dwarf?
Stars that are relatively similar to the size of the sun.
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What happens to stars after the red super giant stage?
They will become a supernova.
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Why can scientists not estimate the mass of starts?
Cannot take the measurements needed and don't have the technology.
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What happens to a star after the main sequence stage, to eventually become a black dwarf?
Star expands to become a red giant, heavier elements formed by fusion, star shrinks to become a white dwarf. Star cools.
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Why is it important that ammeters have a low resistance?
So ammeter affects the current as little as possible.
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What is an advantage of using the same temperature scale in different countries?
It gives a common understanding.
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Why does a skateboard move backwards when the person jumps forwards?
Momentum before jumping = momentum after jumping. Before jumping momentum of skateboard and skateboarder is zero. After jumping skateboarder has momentum forwards so skateboard must have equal momentum backwards.
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What happens in the process of nuclear fission?
Nuclei split.
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In which part of a nuclear power station are isotopes produced?
Nuclear reactor.
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What is meant by the term half life?
Average time taken for number of nuclei to halve.
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What is the risk to the patient of using radioactive medical tracer?
Radiation causes ionisation that may then harm healthy cells.
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Why do doctors frequently use radioactive substances for medical diagnosis?
Benefit of diagnosis greater than risk of radiation.
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Why is it safe for a drill to be fitted with a two core cable rather than a three core cable?
It is double insulated.
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How does an RCCB operate?
Detects a very small difference between the current in the live wire and the current in the neutral wire.
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Why does the resistance of the bulb increase as the potential difference increases?
The temperature of the bulb increases.
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What are the two substances used in nuclear reactors?
Uranium and plutonium.
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How is nuclear fission used to generate electricity?
Energy used to heat water and produce high pressure steam. The steam drives a turbine which turns a generator.
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Why does lowerig the control rods in a nuclear reactor reduce the amount of energy released from the nuclear fuel?
There are fewer neutrons so chain reactions slow down.
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What is meant by thinking distance?
Distance vehicle travels during driver's reaction time.
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What things affect thinking distance?
Tiredness, alcohol, drugs, speed.
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What things affect braking distance?
Icy roads, worn tyres, road surface, condition of the brakes.
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Why does applying the brakes cause the temperature of the brakes to increase?
Work is done by friction between brakes and wheel which causes decrease in KE and increase in thermal energy.
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What is the benefit of a hybrid car being fitted with a regenerative braking system?
The battery needs recharging less often as the efficiency of the car is increased. The decrease in kinetic energy charges the battery up.
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Why should you take a tablet containing non-radioactive isotope of iodine?
Limits amount of iodine that can be absorbed so reducing risk of cancer.
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Why is it not safe to plug an appliance into the mains electricity supply with a 2.5mm copper wire?
Current exceeds maximum safe current for a 2.5mm wire. A 2.5mm wire would overheat.
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What is the structure of the cable that should be used with appliances attatched to the mains electricity supply?
Contains live, neutral and earth wires. Cross sectional area of wires 4mm. Wire should be insulated.
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What is the difference between alternating current and direct current?
AC is constantly changing direction. DC flows in one direction only.
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What form of energy is stored in a stretched spring?
Elastic potential energy.
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What is the limit of proportionality of the spring?
The point where the force and the spring are not directly proportional.
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Why may a person receive a higher than average dose of radiation from background radiation?
May live in altitude, may live in a building made from granite.
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Discuss whether it is ethical to use animals in scientific experiments.
Animals have no choice and so should not be used, better to experiment on animals than humans.
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What is the meaning of electric current?
Flow of electric charge.
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What is the meaning of potential difference?
Work done of charge.
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Why does resistance in the metal in a filament bulb increase with temperature?
Metals contain free electrons. As temperatures of filament increases, ions vibrate faster. Electrons collide more frequently with the ions.
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What is the difference between a protostar and a main sequence star?
A protostar is at a lower temperarure as nuclear fusion reactions have not started.
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How were the different elements in the universe formed?
By nuclear fusion of hydrogen to helium. Elements heavier than iron are formed in a supernova.
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Why should scales not be used immediately after drinking water?
Gives misleading value because high water content changes body resistance.
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Compare the action of a RCCB with the action of a fuse.
RCCB detects difference between current in live and neutral wires. Fuse overheats and melts.
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What is one man made source of background radiation?
Nuclear power stations.
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Why are radioactive readings different?
Radioactive decay is a random process.
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Why are stars stable in the main sequence period of the life cycle?
Forces within the star are balanced.
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Why can't scientists give the exact number of years a star will be in the main sequence period?
Insufficient evidence.
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Why is the rate of nuclear fusion faster in a large star than a small star?
Larger stars have a shorter main sequence period so they must have the faster rate of nuclear fusion since they use up hydrogen at a faster rate.
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What happens when a star bigger than the sun finishes the main sequence period?
The core of the star runs out of hydrogen so star expands to form a red supergiant. The outer layers explode forming a supernova. The elements heavier than iron are formed. The core shrinks becoming a neutron star. If mass big enough - black hole.
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Why does the diode cause the trace on the oscilloscope to change?
Diode has large resistance in one direction so stops current flow in that direction.
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Why does a streamlined car go faster?
Air resistance is smaller so reaches a higher speed.
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What is the frequency of the mains electricity in the UK?
50 Hz.
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What causes the RCCB to switch the circuit off?
Some current flows to Earth and RCCB detects the difference between the current in live and neutral wire.
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What is one advantage of using an RCCB rather than a fuse?
Can be reset.
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How does an increase in temperature affect a thermistor?
Increases temperature of thermistor so changes resistance.
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Describe a distance time graph.
Slope = steady speed. Horizontal line = stopped. Curve up = accelerating. Curve to horizontal = deaccelerating. Slope down = steady speed in other direction.
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What is the formula for acceleration?
Acceleration = change in velocity divided by time taken.
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Describe a velocity time graph.
Upwards slope = acceleration. Horizontal line = steady speed. Downwards slope = deacceleration. Area under any section is distance travelled.
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What is the formula for weight?
Weight (N) = mass (Kg) x gravitational field strength.
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What is the formula for force?
Force = mass x acceleration (m/s squared)
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What is the formula for work done?
Work done = force x distance.
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What is the formula for gravitational potential energy?
Gravitational potential energy = mass x gravity x height.
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What is the formula for kinetic energy?
Kinetic energy = 1/2 x mass x speed squared.
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What is the formula for force of spring?
Force = k (spring constant N/m) x e (extension m).
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What is the formula for power?
Power (Watts) = work done divided by time taken.
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What is the formula for momentum?
Momentum (kg m/s) = mass x velocity
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What is the formula for current?
Current = charge (coulomb) divided by time.
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What is the formula for potential difference?
PD = work done divided by charge OR potential difference = current x resistance.
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Series circuit.
Potential difference is shared. Current is the same everywhere. Resistance adss up. Cell voltages add up.
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Parallel circuits.
PD is the same across all components. Current is shared between branches.
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What is the mains supply and battery supply?
Mains AC. Battery DC.
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How does the earth wire work?
Attatched to the metal casing of the plug and carries the electricity to the earth should something go wrong.
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What is the formula for energy transferred?
Energy transferred = power rating x ime.
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What is the formula for electrical power?
Power = current x potential difference.
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What is the formula for energy transformed?
Energy transformed = charge x potential difference.
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How does alpha radiation change the particle?
Minus 4 from the top number. Minus 2 from the bottom number.
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How does beta radiation change the particle?
Add one to the bottom number.
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How do you work out the half life?
Divide by two.
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What are some uses of radiation?
Medical tracers, treatment of cancer, sterilisation.
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Other cards in this set

Card 2

Front

Why does hair stand on end when someone is electrically charged?

Back

All the charges are the same because the hairs are repelling.

Card 3

Front

Why does a child not become electrically charged when sliding on metal?

Back

Preview of the front of card 3

Card 4

Front

What star becomes a black dwarf?

Back

Preview of the front of card 4

Card 5

Front

What happens to stars after the red super giant stage?

Back

Preview of the front of card 5
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