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Physics > Particals at Work > Flashcards

Particals at Work Flashcards

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1
Q

What does Ohm’s law state?

A

That the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor

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2
Q

Like charges …

A

.. repel

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3
Q

Unlike charges …

A

.. attract

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3
Q

What are two examples of electron transfer between charged objects?

A
  • insulating materials that become positively charged when rubbed lose electrons
  • insulating materials that become negatively charged when rubbed together
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5
Q

What is the role of a switch?

A

A switch enables the current in a circuit to be switched on and off

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6
Q

What is the role of a cell?

A

To push electrons around a complete circuit. A battery consists of two or more cells.

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6
Q

What is the role of an indicator?

A

Eg. A bulb

Designed to emit light as a signal when a current passes through it

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8
Q

The force between two charged objects is a …

A

.. non-contact force

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9
Q

What is the role of a diode?

A

Allows the current to flow through in one direction only

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9
Q

What is the role of an Ammeter?

A

To measure electric current

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10
Q

What is the role of a fixed resistor?

A

To limit the current in a circuit

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12
Q

What is the role of a fuse?

A

Designed to melt and therefore ‘break’ the circuit if the current through it is greater than a certain amount

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13
Q

What is the role of a heater?

A

It’s designed to transfer the energy from an electric current to heat the surroundings

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14
Q

What is the role of a voltmeter?

A

To measure potential difference (eg. Voltage)

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15
Q

What is the role of a variable resistor?

A

To allow the current to be varied

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16
Q

For components in a series circuit …

A
  • the CURRENT is the SAME in each component
  • the total POTENTIAL DIFFERENCE is SHARED between the components
  • adding their resistances gives the total resistance
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17
Q

What is the role of a light-emitting diode (LED)?

A

A diode that emits light when a current passes through it

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18
Q

For components in a parallel …

A
  • the total current is the sum of the currents through the seperate components
  • the POTENTIAL DIFFERENCE across each component is the SAME
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19
Q

What is in a mains circuit?

A
  • a live wire = alternatively positive and negative every cycle
  • neutral wire at zero volts
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20
Q

In a parallel circuit, the bigger the resistance of a component …

A

.. the smaller the current that will pass through that component

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21
Q

What happens when you add more resistors to a parallel circuit?

A

It decreases the total resistance because the total current through the resistors is increased and the total potential difference across them is uncharged

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22
Q

Direct current flows …

A

.. in one direction only

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24
Q

What happens when you add more resistors in a series circuit?

A

it increases the total resistance because the current through the resistors is reduced and the total potential difference across them is unchanged

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24
Q

Alternating current repeatedly …

A

.. reverses its direction flow

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25
Q

The potential difference of an a.c supply is the …

A

.. maximum voltage measured from zero volts

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26
Q

What are socket and plug cases made of?

A
  • Stiff plastic materials that enclose the electrical connections
  • Plastic is used because it is a good electrical insulator
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27
Q

What is a mains cable made up of?

A
  • two or three insulated copper wires surrounded by an outer layer of flexible plastic material
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28
Q

What is in a three-pin plug/ three-core cable?

A
  • a brown live wire
  • a blue neutral wire
  • a striped green and yellow earth wire
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29
Q

What is the earth wire connected to?

A

The longest pin in a plug and is used to earth the metal case of mains appliance

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30
Q

The power supplied to a device is …

A

.. the energy transferred to it each second

31
Q

What happens if you increase the temperature of a substance?

A

Its internal energy increases

32
Q

What happens when charge flows around a circuit?

A

The energy supplied by the battery is equal to the energy transferred to all the components in the circuit

32
Q

What are the particals like in a solid?

A
  • they’re held next to eachother

- they are the least energetic of the states of matter

33
Q

What are the particals like in a liquid?

A
  • They move about at random
  • They are in contact with eachother
  • They are more energetic than particals in a solid
34
Q

What are the particals like in a gas?

A
  • Move around randomly
  • They are far apart
  • Much less dense than solids and liquids
  • The most energetic of all states of matter
35
Q

What happens when a substance changes state?

A

Its mass stays the same because the number of particals stays the same

36
Q

For a pure substance …

A
  • its melting point is the temperature at which it melts

- its boiling point is the temperature at which it boils

38
Q

What determines the state of a substance?

A

The strength of the forces of attraction between its particals

39
Q

The pressure of a gas on a surface is caused by …

A

.. the particals of the gas repeatedly hitting the surface

40
Q

What is the Specific latent heat of fusion?

A

The energy needed to melt 1kg of a substance without changing its temperature

41
Q

What causes the pressure of a gas?

A

The random impacts of gas molecules on surfaces that are in contact with the gas

42
Q

What does a domestic electricity meter do?

A

Measures how much energy is supplied

43
Q

What can radioactive isotopes be used for?

A

In medicine for medical imaging

  • treatment of cancer
  • as tracers to monitor organs
44
Q

What are the properties of Gamma radiation?

A
  • stopped by thick lead
  • have an unlimited range
  • consists of electromagnetic radiation
  • the least ionising power
45
Q

What is Latent heat?

A

The energy needed for a substance to change its state without changing its temperature

46
Q

Why does the pressure of the gas in a sealed container increase when the temperature increase?

A
  • the molecules move faster so the hit the surfaces with more force
  • the number of impacts per second increases so the total force of the impacts increases
47
Q

For a fixed mass of gas at a constant temperature …

A
  • its pressure increases if its volume decreases

- reducing the volume, increases the number of molecular impacts per second

48
Q

The temperature of a gas can increase if …

A

.. it is compressed rapidly because work is done on it and energy isn’t transferred to its surroundings quickly enough

49
Q

Radioactive substances contain …

A

.. unstable nuclei that become stable bt emitting radiation

50
Q

What are the three main types of radiation?

A
  • Alpha
  • Beta
  • Gamma
50
Q

What is the Plum Pudding model?

A
  • positively charged matter evenly spread about = the pudding
  • electrons burried inside = the plums
51
Q

When does radioactive decay occur?

A
  • it is a random event

- you cannot predict or influence when it will happen

51
Q

Where is most of the atom’s mass located?

A

In the central nucleus where the atom has a small positive charge

52
Q

What is an isotope of an element?

A

Atoms with

  • the same number of protons
  • different numbers of neutrons
  • the same atomic number
  • different mass numbers
53
Q

What happens in alpha decay?

A
  • nucleus loses 2 protons and 2 neutrons

- 2 protons and 2 neutrons are emitted as an alpha partical

54
Q

What happens in beta decay?

A
  • a neutron in the nucleus changes into a proton

- an electron is created in the nucleus and instantly emitted

56
Q

What happens when a substance is heated?

A
  • if its temperature increases, the kinetic energy of its particals increases
  • if it melts or boils, the potential energy of its particals increases
58
Q

What are the properties of Alpha particals?

A
  • stopped by paper
  • have a range of a few centimetres
  • consists of particals = two protons and two neutrons
  • the greatest ionising power
59
Q

What are the properties of Beta particals?

A
  • stopped by a thin sheet of metal
  • has a range of about one metre
  • consists of fast moving electrons emitted from the nucleus
  • more ionising than Gamma radiation
60
Q

What happens in a nuclear reactor?

A

The control rods absorb fission neutrons to ensure that, on average, only one neutron per fission goes on to produce further fission.

61
Q

What did Rutherford do?

A
  • used alpha particals to probe atoms

- he found some of the particals were scattered through large angles

62
Q

What do Alpha, Beta and Gamma radiation do when they pass through substances?

A
  • they ionise them

- ionisation in a living cell can damage or kill the cell

64
Q

What is the half-life of a radioactive isotope?

A

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

65
Q

How do you tell how useful a radioactive isotope is?

A
  • its half-life

- the type of radiation it gives out

66
Q

What is nuclear fission?

A

The splitting of an atom’s nucleus into two smaller nuclei and release of two or three neutrons and energy

67
Q

When does induced fission occur?

A

When a neutron is absorbed by a uranium-235 nucleus or a plutonium-239 nucleus and the nucleus splits

67
Q

Where does a chain reaction occur?

A

In a nuclear reactor when each fission event causes further fission events

68
Q

Where and how is nuclear waste stored?

A
  • in safe and secure conditions

- for many years

69
Q

What is nuclear fission?

A

The process of forcing the nuclei of two atoms close enough together so that they form a single larger nucleus.

69
Q

What condition is needed for nuclear fission to take place?

A
  • very high temperatures

- this is because the nuclei to be fused are difficult to contain

70
Q

What is radon gas?

A

An alpha emitting isotope that seeps into houses though the ground in some areas

71
Q

Why is radioactive Nuclear waste dangerous?

A

It can cause cancer

73
Q

What happens when two light nuclei are fused together?

A

Energy is released

Physics (5 decks)

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