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Particals at Work Flashcards

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
The potential difference of an a.c supply is the ...
.. maximum voltage measured from zero volts
26
What are socket and plug cases made of?
- Stiff plastic materials that enclose the electrical connections - Plastic is used because it is a good electrical insulator
27
What is a mains cable made up of?
- two or three insulated copper wires surrounded by an outer layer of flexible plastic material
28
What is in a three-pin plug/ three-core cable?
- a brown live wire - a blue neutral wire - a striped green and yellow earth wire
29
What is the earth wire connected to?
The longest pin in a plug and is used to earth the metal case of mains appliance
30
The power supplied to a device is ...
.. the energy transferred to it each second
31
What happens if you increase the temperature of a substance?
Its internal energy increases
32
What happens when charge flows around a circuit?
The energy supplied by the battery is equal to the energy transferred to all the components in the circuit
32
What are the particals like in a solid?
- they're held next to eachother | - they are the least energetic of the states of matter
33
What are the particals like in a liquid?
- They move about at random - They are in contact with eachother - They are more energetic than particals in a solid
34
What are the particals like in a gas?
- Move around randomly - They are far apart - Much less dense than solids and liquids - The most energetic of all states of matter
35
What happens when a substance changes state?
Its mass stays the same because the number of particals stays the same
36
For a pure substance ...
- its melting point is the temperature at which it melts | - its boiling point is the temperature at which it boils
38
What determines the state of a substance?
The strength of the forces of attraction between its particals
39
The pressure of a gas on a surface is caused by ...
.. the particals of the gas repeatedly hitting the surface
40
What is the Specific latent heat of fusion?
The energy needed to melt 1kg of a substance without changing its temperature
41
What causes the pressure of a gas?
The random impacts of gas molecules on surfaces that are in contact with the gas
42
What does a domestic electricity meter do?
Measures how much energy is supplied
43
What can radioactive isotopes be used for?
In medicine for medical imaging - treatment of cancer - as tracers to monitor organs
44
What are the properties of Gamma radiation?
- stopped by thick lead - have an unlimited range - consists of electromagnetic radiation - the least ionising power
45
What is Latent heat?
The energy needed for a substance to change its state without changing its temperature
46
Why does the pressure of the gas in a sealed container increase when the temperature increase?
- 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
For a fixed mass of gas at a constant temperature ...
- its pressure increases if its volume decreases | - reducing the volume, increases the number of molecular impacts per second
48
The temperature of a gas can increase if ...
.. it is compressed rapidly because work is done on it and energy isn't transferred to its surroundings quickly enough
49
Radioactive substances contain ...
.. unstable nuclei that become stable bt emitting radiation
50
What are the three main types of radiation?
- Alpha - Beta - Gamma
50
What is the Plum Pudding model?
- positively charged matter evenly spread about = the pudding - electrons burried inside = the plums
51
When does radioactive decay occur?
- it is a random event | - you cannot predict or influence when it will happen
51
Where is most of the atom's mass located?
In the central nucleus where the atom has a small positive charge
52
What is an isotope of an element?
Atoms with - the same number of protons - different numbers of neutrons - the same atomic number - different mass numbers
53
What happens in alpha decay?
- nucleus loses 2 protons and 2 neutrons | - 2 protons and 2 neutrons are emitted as an alpha partical
54
What happens in beta decay?
- a neutron in the nucleus changes into a proton | - an electron is created in the nucleus and instantly emitted
56
What happens when a substance is heated?
- if its temperature increases, the kinetic energy of its particals increases - if it melts or boils, the potential energy of its particals increases
58
What are the properties of Alpha particals?
- stopped by paper - have a range of a few centimetres - consists of particals = two protons and two neutrons - the greatest ionising power
59
What are the properties of Beta particals?
- 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
What happens in a nuclear reactor?
The control rods absorb fission neutrons to ensure that, on average, only one neutron per fission goes on to produce further fission.
61
What did Rutherford do?
- used alpha particals to probe atoms | - he found some of the particals were scattered through large angles
62
What do Alpha, Beta and Gamma radiation do when they pass through substances?
- they ionise them | - ionisation in a living cell can damage or kill the cell
64
What is the half-life of a radioactive isotope?
The average time it takes for the number of nuclei of the isotope in a sample to halve
65
How do you tell how useful a radioactive isotope is?
- its half-life | - the type of radiation it gives out
66
What is nuclear fission?
The splitting of an atom's nucleus into two smaller nuclei and release of two or three neutrons and energy
67
When does induced fission occur?
When a neutron is absorbed by a uranium-235 nucleus or a plutonium-239 nucleus and the nucleus splits
67
Where does a chain reaction occur?
In a nuclear reactor when each fission event causes further fission events
68
Where and how is nuclear waste stored?
- in safe and secure conditions | - for many years
69
What is nuclear fission?
The process of forcing the nuclei of two atoms close enough together so that they form a single larger nucleus.
69
What condition is needed for nuclear fission to take place?
- very high temperatures | - this is because the nuclei to be fused are difficult to contain
70
What is radon gas?
An alpha emitting isotope that seeps into houses though the ground in some areas
71
Why is radioactive Nuclear waste dangerous?
It can cause cancer
73
What happens when two light nuclei are fused together?
Energy is released

Physics (5 decks)

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