Physics P2B

Direct current
runs off battery // phone laptop torch // flows in one direction only
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AC Alternating current
constantly changing direction // supplied by main socket // in cycles = freq
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how to measure voltage / P.D.
Oscilloscope
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Plugs and cables
3 core cable (kettle) each wire has plastic insulating cover around copper wire as copper is a good conductor // 2 core cable (hair dryer - neutral and live only)
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3 pin plug features safety [4]
tough plastic case so its a good insulator and doesn't break // cable made of plastic so dissent break easy // cable grip - keeps cable in plover to precept wires coming out // Fuse - melts f current gets too high.g. 5A fuse carries fuse UP TO 5amps
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Live wire
right side and brown
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neutral wire
left and blue
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earth wire
green and yellow and in middle
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2 core cable
no live wire // used for double insulated products (outer casing isn't metal) - hairdryer
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3 core cable
appliances w metal casing - kettle, washing machines and toasters
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Live wire
v dangerous - gives electrical shock - avoid this with earth wire
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Double insulated applaince
No earth wire bc no way live could get in touch with casing
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Kettle example
Live wire becomes lose and touches casing so whole metal case becomes live and can give shock. large current goes from live wire to earth wire which has a low resistance so current goes up and blows fuse
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How does earth wire prevent shocks
Also connected to outer casing, if live wire comes in contact with metal casing current is directed through earth wire back into plug then earth
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RCCB
Gives another layer of protection for CERTAIN circuits. Detects changed current between live and neutral wire. Much faster than fuse and can be rest. Cuts off current quicker than fuse
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Current and heat [3]
When current flows through a resistor the temperature rises so wire carrying the current becomes warmer. thinner wire = warmer THICKER = less warm.
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Laptop example of current and heat
Laptop has thinner cable that supplies electricity to it. Has a lower current so less heating effect on cable
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Washing machine example
higher current s it has a thicker cable to reduce the heating effect
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Fialment lamp example
THIN filament running through its which gets very hot so IT GLOWS. Produces light. heat is wasted to environment s is not efficient
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CFL
More efficient generates less heat so less waste energy. Contributes less to co2 emissions But ;less efficient = cheaper?
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background radiation
Radioactivity comes from the nucleus - ALPHA, GAMMA AND BETA. Isotopes tend to be radioactive - decay into other elements and give out radiation
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geiger muller tube
Measures amount of radioactivity from a substance in counts per min. HIGHER COUNT = More radioactive
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Background radiation
Natural, comes from environment in low amounts so is harmless
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Background radiation sources
Air - radon gas 50% Food and drink // Rocks and ground // cosmic rays - space // Man made sources: fallout from nuclear weapon tests, nuclear waste and nuclear accidents
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Radiographers
lead aprons, screen protect from exposure. Uranium miners - protective clothing + face masks Miners = due to all rocks
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Plum pudding background info and theory
Rutherford and marsden 1900s thought is was nucleus w positive charge and electrons stuck in it
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Plum pudding experiment
Thin layer of gold foil, Fired stream of alpha particles (2 protons and 2 neutron - overall positive charge 2+) Set up in vacuum chamber: no air so alpha particles couldn't bump into air particles.// Detector used to detect where alpha particles go
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Expectation of experiment
alpha partciles go straight through
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Reality / outcome of experiment
Most went straight through // some were deflected by varying amounts // some came straight back
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Conclusion
Most passed through bc MOST OF ATOM IS EMPTY SPACE .// some selected bc POSITIVE CENTRE TO ATOMS // some came back bc POSITIVE CENTRE IS V DENSE
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What is nuclear radiation
V RANDOM - CANNOT PREDICT // alpha beta and gamma - emitted from nucleus of an unstable atom
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Alpha [6]
2 neutrons and 2 protons = HELIUM NUCLEUS // Big heavy and slow moving // Charge = 2+// Mass = 4 // Strongly ionising / Stopped by paper/skin weak penetration
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Beta [5]
Electron ejected from nucleus // negative charge // neutron broken down into electron // Charge = -1 mass = too tiny so MODERATELY IONSIING. Stopped by few mm aluminium
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Gamma [6]
No mass or charge / em wave // emitted from nucleus of radioactive element // v far range // v large penetration // weakly ionising - tends to pass through than collide w atom
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Deflection in electric and magnetic fields
Alpha and beta both deflected in magnetic / electric field but in opposite directions due to their opposite charge. Alpha = larger charge than beta and greater force in fields but gets deflected less due to greater mass. BETA DEFLECTED MOST. Gamma no
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Thorium / alpha
Mass number = -4 ATOMIC NO. = -2 /////////// 228 TH 90 SO AFTER EJECTING ALPHA U LOSE 2 PROTONS
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Potassium / beta
mass no - doesn't change // atomic no = +1
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radioactive definition
an unstable nucleus with too much energy which decays
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Half life meaning
average time it takes of the no. if nuclei i a radioactive isotope sample to halve ( RADIOACTIVITY OF A SAMPLE DECREASES OVER TIME)
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Half life explanation
each time decay happens alpha, gamma and beta is given out so one more radioactive nucleus has dissapeared // Older a sample becomes the less radiation it will emit. RANDOM = Cant predict when but can measure time taken for radioactive nuclei to hlav
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Other cards in this set

Card 2

Front

AC Alternating current

Back

constantly changing direction // supplied by main socket // in cycles = freq

Card 3

Front

how to measure voltage / P.D.

Back

Preview of the front of card 3

Card 4

Front

Plugs and cables

Back

Preview of the front of card 4

Card 5

Front

3 pin plug features safety [4]

Back

Preview of the front of card 5
View more cards

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