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Physics > 2b) Electricity and The Atom > Flashcards

2b) Electricity and The Atom Flashcards

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0
Q

What is the UK mains supply (approximately)?

A

230v

Alternating Current supply (AC)

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1
Q

What is an electric current?

A

Movement if charge carriers

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2
Q

What is the frequency if the AC mains supply?

A

50 cycles per second

50 Hz

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3
Q

What is AC and DC?

A

Alternating Current - mains supply
Current is constantly changing direction

Direct Current - cells/batteries
Current flows in the same direction

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4
Q

How can you work out the frequency of a supply?

A

Frequency = 1/time period

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5
Q

What is a time period on an oscilloscope?

A

Time taken to complete one cycle

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6
Q

What do the gain dial and time base dial control on an oscilloscope?

A

Gain dial - how many volts each centimetre division represents on the vertical axis
Time base dial - how many milliseconds each division represents on the horizontal axis

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7
Q

How much is one millisecond in seconds?

A

1ms = 0.001s

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8
Q

What are the metal parts of a plug made out if and why?

A

Copper or brass

Very good conductors

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9
Q

What is the case, cable grip and cable insulation made out of and why?

A

Rubber or plastic

Good insulators and flexible

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10
Q

What 3 coloured wires do most cables have?

A

Brown live wire - alternates current from positive and negative voltage
Blue neutral wire - 0v
Earth wire - carries electricity to Earth for safety and to prevent fires and shocks

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11
Q

What does earthing mean?

A

Case must be attached to an earth wire which can never become live
All appliances with metal cases are earthed to reduce risk of electric shock

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12
Q

When is an appliance double insulated?

A

If the appliance has a plastic casing and no metal parts showing

Doesn’t need an earth wire
Only live and neutral (two-core cables)

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13
Q

What is a circuit breaker?

A

An electrical safety device which protect the circuit from damage if too much current flows

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14
Q

What does an RCCB stand for?

A

Residual Current Circuit Breaker

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15
Q

Why are circuit breakers better than fuses?

A

Easily reset by flicking a switch
More convenient than fuses which gave to be replaced
Even work for small current changes which aren’t big enough to melt a fuse
Quicker - safer

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16
Q

What is an isotope?

A

Different forms of the same element

Atoms with the same number of protons but a different number of neutrons

17
Q

What does it mean by an isotope is radioactive?

A

It decays into other elements and gives out radiation

18
Q

What is background radiation?

A

Radiation that is present at all times, all around us

19
Q

Where does the background radiation we receive come from?

A

Naturally occurring isotopes around us - in the air, in fold, in rocks etc.
From cosmic rays mostly from the sun in space
Due to man-made sources - nuclear accidents like Chernobyl or dumped waste

20
Q

What are the three types of radiation?

A

Alpha
Beta
Gamma

21
Q

Describe an alpha particle

A 
Two neutrons and two protons
Same as helium nucleus
Relatively big, heavy, slow moving
Don't penetrate very far into materials and are stopped quickly
Strongly ionising
22
Q

What does the term ionising mean?

A

When atoms bash into other atoms and knock electrons off them

23
Q

Describe beta particles

A 
They are Electrons 
Move quite fast and are small
Penetrate moderately into materials 
Moderately ionising
Long range in air
Virtually no mass
Charge of -1
24
Q

What happens in the nucleus when a b-particle is emitted?

A

For every b-particle emitted, a neutron turns into a proton in the nucleus

25
Q

Describe gamma rays

A

Opposite of alpha particles
Penetrate far into materials without being stopped
Pass straight through air
Weakly ionising - tend to pass through atoms rather than collide
No mass and no charge
Very short wavelength EM waves

26
Q

What happens when a nucleus decays by alpha emission?

A

It’s atomic number decreases by two (two less protons)

It’s mass number decreases by four (two less electrons as well as protons)

27
Q

What happens when a nucleus decays by alpha emission?

A

Increases the atomic number by one (one more proton)

Mass number doesn’t change (same electrons and same neutrons)

28
Q

What is a half-life?

A

The average time it takes for the number of nuclei in a radioactive isotope to halve

29
Q

How can nuclear industry workers ensure they aren’t being exposed to too much radiation?

A

Wearing protective clothing and face masks to stop them touching or inhaling radioactive material
Monitor their radiation doses through regular check-ups

30
Q

How can radiographers ensure they aren’t being exposed to too much radiation?

A

Wearing lead aprons

Stand behind lead screen to protect them from prolonged exposure to radiation

31
Q

What does radiation dose or the amount of radiation your exposed to depend on?

A

Location - underground rocks release radioactive radon gas, high altitudes have more exposure to cosmic rays
Occupation - nuclear industry workers, radiographer, miners and pilots have higher risks

32
Q

Describe the charges on each type of radiation

A

Alpha: positive charge
Beta: negative charge
Gamma: no charge (neutral)

33
Q

What happens to each type of radiation when travelling through a magnetic or electric field?

A

Both alpha and beta particles deflected but in opposite ways
Alpha particles deflected less because they have a larger mass
Gamma has no charge so it doesn’t get deflected

34
Q

What is the unit for measuring radioactivity?

A

Becquerel (Bq)

1 Bq means one nucleus decaying per second

35
Q

What happens to the radioactivity of a sample over time?

A

It decreases

36
Q

What is the count rate?

A

Number of radioactive emissions detected per unit of time

37
Q

What is nuclear fission?

A

Splitting up of big atomic nuclei

38
Q

What is nuclear fusion?

A

Joining up of small atomic nuclei

Happens in the sun

39
Q

State some uses of radiation

A

Smoke detectors - alpha
Tracers on medicine - short life beta or gamma
Radiotherapy - treatment of cancer - gamma
Sterilisation - gamma

40
Q

Life cycle of a star bigger than the sun

A 
Protostar
Main sequence star
Red super giant
Supernova
Neutron star
Black hole
41
Q

Life cycle of a star same size as the sun

A 
Protostar
Main sequence star
Red giant
White dwarf
Black dwarf

Physics (6 decks)

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