Physics 2

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What is Static Electricity?
When charges are not free to move which causes them to build up in one place.
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How does Static electricty caused?
By friction of two insulating materials.
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Can you explain electron transfer?
2 insulating materials are rubbed together causing friction. Electrons will move off one material to the other, leaving one material negatively charged and one positively charged.
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In which direction do the electrons move when a polythene rod is rubbed against a cloth?
From the duster to the rod.
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What moves - the electrons or the charge?
The electrons.
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True or false - Opposite charges attract and like charges repel?
True.
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What is Current and what is it measured in?
The flow of electric charge around a circuit. Amps.
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When can Current flow?
Only when there is a potential difference across that component.
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What is Potential difference and what is it measured in?
The driving force that pushes the current around. It is also the work down between two points in a circuit per unit of charge. Volts.
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What is Resistance and what is it measured in?
It's anything in the circuit which slows the flow down. Ohms.
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What is the link between Resistance and Current (+potential difference)?
The greater the resistance the smaller the current that flows for a given potential difference across the component.
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How do you measure (with what equipment too) the Resistance in a circuit?
Measure the current through and the potential difference across the component. Use a variable resistor, ammeter, component, a voltmeter (in parallel) and a cell.
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What piece of measuring equipment is to be put in series with a component?
Ammeter.
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What does the variable resistor vary and what does it allow you to do?
The current flowing through the circuit and allows you to take several pairs of reading from the ammeter and voltmeter.
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What is the convention direction of electron transfer?
Positive to negative (but actually negative to positive!)
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Can you describe what a Current/P.D-Resistor graph looks like?
A straight line - the current is directly proportional to the P.D.
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Can you describe what a Current/P.D-Filament lamp graph looks like?
A curved line (like a very thin 'S'). As the temperature increases, the resistance increases.
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Can you describe what a Current/P.D-Diode graph looks like?
Horizontal line then at about 2 goes straight up. This is because current will only flow in one direction through a diode. The diode has a very high resistance in the opposite direction.
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Does Resistance increase or decrease with temperature?
Increase.
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Why is this?
As electrical charge flows through a resistor some energy is transferred into heat energy so the resistor gets hot.The heat energy causes the ions in the conductor to vibrate more making it harder for the charged particles to get through the resistor
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In straight line graphs, how does the steepness show the amount of resistance?
The steeper the line the lower the resistance.
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What is a Diode made out of?
A semiconductor material such as silicon.
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What does a Diode do?
Only allows current to flow in one direction.
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What is a Diode used for?
To regulate the potential difference in circuits and is very useful in Electronic circuits.
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What does a Light-Emitting Diode do?
Emits light when a current flows through it in the forward direction.
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Why are LED's getting used more often in lighting?
They use a much smaller current so use less energy.
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What are LED's used for?
Appliances to show that they're switched one (e.g TV's), digital clocks, traffic lights and remote controls.
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What is a Light-Dependent Resistor and how does it work?
It's a resistor that depends on light. As the light intensity increases, the resistance falls. In darkness, the resistance is highest.
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What are LDR's used for?
Automatic night lights and burglar detectors.
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How does the resistance of a Thermistor vary as temperature varies?
The resistance decreases as the temperature increases.
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What are Thermistors used for?
Temperature detectors, car engine temperature sensors and electronic thermostats.
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What happens if one component in a series circuit is broken?
Everything else in the circuit will not work.
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Is potential difference shared or the same in a series circuit?
Shared. SPS
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Is current shared or the same in a series circuit?
The same anywhere. SCA.
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How do you work out the Total Resistance in a series circuit?
Add up all resistances.
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What types of circuits are used in everyday life?
Parallel.
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What is the only household component wired in Series?
Christmas Fairy lights.
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What are the two reasons for a car to be connected in Parallel?
Everything has to be turned on and off seperately.
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How many volts is the UK mains supply?
230V.
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What does AC supply mean?
That the current is constantly changing direction?
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Which ones match up - Battery and Mains Supply to AC or DC?
Battery = DC. Mains Supply = AC.
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What is the frequency of the AC mains supply?
50 cycles per second/50Hz.
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What trace will you see if you plug a DC supply into an oscilloscope?
A straight line.
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What does the vertical height of the AC trace show?
The input voltage.
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What does the Gain dial control?
How many volts each centimetre division represents on the vertical axis.
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What does the Timebase dial control?
How many milliseconds each division represents on the horizontal axis.
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What equation do you use to work out the frequency?
1 over time period (s)
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What are 9 examples of electricity hazards of the home?
Long cables, frayed cables, cables in contact with something hot or wet, water near sockets, shoving things into sockets, damaged plugs, too many plugs in one socket, lighting sockets without bulbs and appliances without covers on.
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What is the Live wire?
The brown wire in a mains supply alternate between positive and negative voltage.
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What is the Neutral wire?
The blue wire which is always at 0Volts.
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What is the Earth wire?
The green and yellow wire which protects the wiring. It is there for safety as it works with the fuse to prevent fire and shocks. It's attached to the metal casing of the plug and carries electricity to the earth if something goes wrong.
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What do thicker cables allow?
They have less resistance so more current can flow through them.
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What are the 2 features of plugs?
The metal parts are made of copper/brass because they're great conductors. The case, cable grip and cable insulation are made of rubber or plastic because they're good insulators and are flexible.
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What does Earthing and Fuses prevent?
Electric overloads.
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How do Fuses work?
A fault occurs which allows the live wire to touch the metal case. Big current flows through the live wire, through the case and out the earth wire. Big current surge to earth. Surge in current melts fuse which isolates the appliance from the live.
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What does Earthing mean?
That the metal case is attached to an earth wire.
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What does Double Insulation mean and what don't they need?
When the appliance has a plastic casing with no metal parts. It doesn't need an earth wire.
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What do Circuit breakers do?
They detect a current surge in a circuit and break the circuit by opening a switch.
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What advantages do Circuit Breakers have over Fuses?
They're more convenient as you only have to flick a switch to replace them instead of replacing a fuse. They work faster which means they're safer. They detect even the smallest change in current too!
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What advantages do Fuses have over Circuit Breakers?
They are cheaper.
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What type of energy do Resistors produce?
Heat energy.
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What makes an appliance efficient?
It wastes less energy.
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Who came up with the Plum Pudding theory and what was it?
JJ Thomson and that atoms were spheres of positive charge with tiny electrons stuck in them like a plum pudding.
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Who were the 2 scientists who questioned the Plum Pudding model?
Rutherford and Marsden.
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What experiment did they do to test the Plum pudding model?
They fired a beam of alpha particles at a thin gold foil.
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What happened in their experiment?
Most of the particles went straight through but the odd few bounced back. This meant they hit the nucleus and got repelled from the protons.
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What do unstable isotopes do?
Become radioactive by decaying into other elements and give out radiation.
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What are the 3 types of radiation called?
Alpha, Beta and Gamma
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What are the 3 sources of Background radiation?
Naturally occuring unstable isotopes (air, rocks, building materials), radiation from space and man made sources such as fallout from nuclear weapon tests.
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What does Ionising mean?
Atoms bash into other atoms knocking electrons off them before they slow down which creates a lot of ions.
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What are the properties of an Alpha particle?
They have 2 protons and 2 neutrons - the same as a helium nucleus. They're relatively big, heavy and slow moving. They don't penetrate very far into materials and are strongly ionising.
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What are the properties of Beta particles?
They're quite fast and small, they're electrons, they penetrate moderately into materials and are moderately ionising. It has virtually no mass and a negative charge of -1.
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What happens every time a Beta Particle is emitted?
A neutron turns into a proton.
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What are the properties of Gamma rays?
They penetrate far into materials, they're weakly ionising, they have no mass or charge and have very short wavelengths on the EM spectrum.
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What does damage caused by radiation depend on?
The radiation dose.
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What will happen to you if you're exposed to a high radiation dose?
You're likely to develop cancer.
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How can your Location affect the amount of radiation you're exposed to?
Certain underground rocks can cause high levels as they can release radon gas which can get trapped in people's houses. At high altitudes the background radiation increases because of more exposure to cosmic rays.
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How can your Occupation affect the amount of radiation you're exposed to?
Nuclear industry and uranium miners are exposed to 10 times the amount of radiation than normal. Radiographers in hospitals working with with radiation are also exposed. Miners underground can also be highly exposed due to radiation in rocks.
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What can people do to protect themselves from it?
Nuclear industry workers wear protective clothing, face masks to stop them touching/inhaling radioactive material. Radiographers wear lead aprons and stand behind lead screens.
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What happens when Alpha, Beta and Gamma pass through a magnetic field?
Alpha and Beta are deflected in opposite directions because they have opposite charges. Gamma isn't deflected because it has no charge.
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Why isn't Alpha deflected the most?
Although it has a larger charge and feel a greater force, they have a larger mass so don't.
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What is the unit for measuring radioactivity?
Becquerel. (Bq)
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What does 2Bq mean?
Two nuclei decay per second.
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What is the definition on Half-Life?
Half-Life is the average time it takes for the number of nuclei in a radioactive isotope sample to halve.
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How do Smoke alarms work?
A weak source of alpha radiation is placed in the detector close to two electrodes. The source causes ionisation so a current flows. If there is smoke then the smoke will absorb the radiation so the current stops and the alarm sounds.
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What types of radiation are used in the body and why?
Gamma or Beta so that the radiation passes out of the body after a few hours and the radioactivity disappears (short half life).
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Why are Gamma rays used to treat cancer?
It kills all living cells.
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Why is Food exposed to a high dose of Gamma rays?
It kills all the microbes which keeps the food fresher for longer.
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What did Marie Curie discover in 1898?
That radium was radioactive.
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How does Cancer form?
Radiation hits the nucleus of a cell which damages it . The number of mutant cells rise as they divide uncontrollably.
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Why isn't Alpha radiation dangerous outside the body?
It can't penetrate through skin so can't enter your body and harm your organs.
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What is Alpha source most dangerous inside the body?
They can highly damage one area as they're highly ionising. Gamma and Beta usually pass straight out the body.
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What are the Safety precautions when handling Radioactive substances?
Only be exposed for a short time, don't put it in contact with the skin, keep at an arm's length and pointing away from the body and store sources in lead as it absorbs all 3 sources.
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How do Nuclear power stations work?
Atomic nuclei split up and release heat energy. This heat is then used to heat water to make steam which drives a steam turbine connected to an electricity generator. The ‘fuel’ that’s split is either uranium-235 or plutonium-239.
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How does Nuclear fission happen?
A slow moving neutron must be absorbed into a uranium or plutonium nucleus. This makes the nucleus unstable so it splits. Each time it splits, it spits out two or three neutrons which will then hit another nucleus which keeps the chain reaction going
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What does Nuclear fission give out?
Lots of energy.
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Why is the disposal of Nuclear power waste difficult?
The products left over are highly radioactive so can’t be thrown away. It’s very hard and expensive to dispose them safely.
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What are the other problems with Nuclear power?
Although Nuclear fuel is cheap, the overall cost of Nuclear power is high due to the cost of the power plant and final decommissioning. Radiation leaks can also cause catastrophes.
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What is Nuclear Fusion?
Two light nuclei (e.g. hydrogen) can join to create a larger nucleus.
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What releases more energy – Fusion or Fission?
Fusion.
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Why is Fusion better than Fission?
It doesn’t leave a lot of radioactive waste and there’s lots of hydrogen around to use as fuel.
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What are the problems of Nuclear Fusion?
It only works at extremely high temperatures – 10,000,000 degrees! This means you need a really strong magnetic field for it to work.
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How do Protostars form?
The force of gravity makes the clouds of dust and gas spiral together to form a protostar.
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How are Stars born?
Gravitational energy is converted into heat energy so the temperature rises. When the temperature get high enough, hydrogen and helium nuclei undergo nuclear fusion to form helium nuclei which give out massive amounts of heat and light.
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What is the Main sequence star?
The star enters a long stable period where the heat created by the nuclear fusion provides an outward pressure to balance the force of gravity pulling everything inwards. This lasts for billions of years b/c massive amounts of hydrogen it consumes.
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What happens after the Main sequence?
The hydrogen begins to run out. Heavier elements such as iron are made by nuclear fusion of helium. The star then swells into a Red giant or a Red Super giant if it’s big.
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Why does it become red?
Because the surface cools.
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What happens after the Red Giant?
It becomes unstable and ejects and outer layer of dust and gas as a Planetary Nebula. This leaves behind a hot, dense, solid core which is a White Dwarf. This cools to form a Black dwarf and disappears.
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What happens after a Red Super giant?
They glow brightly as they undergo more nuclear fusion and expand and contract several times, forming heavy elements. Eventually they explode as a Supernova forming heavy elements and ejecting them into the universe to form new planets & stars.
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What happens after a Supernova?
The supernova throws outer layers of dust and gas into space leaving a very dense core called a Neutron star. If the star is big enough it becomes a Black hole.
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What are speed and velocity measured in?
Metres per second. m/s.
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What is Speed?
How fast you’re going.
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What is Velocity?
The speed you are going in a certain direction.
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What is Acceleration?
How quickly velocity is changing.
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What 2 effects does Gravity have?
Gives everything a weight and makes all things accelerate towards the ground at 10m/s².
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Other cards in this set

Card 2

Front

How does Static electricty caused?

Back

By friction of two insulating materials.

Card 3

Front

Can you explain electron transfer?

Back

Preview of the front of card 3

Card 4

Front

In which direction do the electrons move when a polythene rod is rubbed against a cloth?

Back

Preview of the front of card 4

Card 5

Front

What moves - the electrons or the charge?

Back

Preview of the front of card 5
View more cards

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niambbii

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This is good for Electricity and Nuclear revision, only has about four cards on forces.

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