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LST > Physics Paper 1 > Flashcards

Physics Paper 1 Flashcards

1
Q

What is a system?

A

an object or group of objects

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2
Q

State 5 energy stores

A

Any 5 from: Kinetic, thermal, gravitational potential, elastic potential, nuclear, magnetic, electrostatic, chemical

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3
Q

Fill in the blank. When a system changes _________ is transferred.

A

Energy

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4
Q

Describe three ways in which energy can be transferred.

A

Heating, force doing work, by moving charges doing work, radiation

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5
Q

Describe the energy transfers that take place when a ball is thrown upwards.

A

A force is exerted by a person to throw a ball upwards.
This causes a transfer in energy from the chemical energy store of the person’s arm, to the kinetic energy store of the ball.

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6
Q

Describe the energy transfers that take place when a car’s brakes are applied.

A

When the brakes are applied, friction force does work.

This causes a transfer in energy from the kinetic energy store of the wheel to the thermal energy store of the brakes.

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7
Q

Describe the energy transfers that take place when a ball is dropped from a height.

A

Gravitational force does work.
This causes a transfer in energy from the gravitational potential energy store of the ball, to the kinetic energy store of the ball.

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8
Q

Describe the energy transfers that take place when water it boiled in an electric kettle.

A

Energy is transferred from the thermal energy store of the heating element in the kettle, to the thermal energy store of the water by heating.

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9
Q

A battery has energy its ___________ energy store.

A

chemical

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10
Q

Food has energy its ___________ energy store.

A

chemical

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11
Q

A moving object has energy its ___________ energy store.

A

kinetic

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12
Q

What is meant by gravitational potential energy store?

A

energy stored in objects raised up against the force of gravity.

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13
Q

A rock at the top of a hill has energy stored in its ___________ energy store.

A

gravitational potential

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14
Q

What is meant by elastic potential energy store?

A

Energy stored in an object which has been stretched or compressed.

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15
Q

A compressed spring has energy its ___________ energy store.

A

elastic potential

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16
Q

An inflated balloon has energy its ___________ energy store.

A

elastic potential

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17
Q

State the equation to calculate kinetic energy.

A

Ek= 0.5mv2

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18
Q

State the equation to calculate gravitational potential energy.

A

Ep =mgh

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19
Q

State the equation to calculate elastic potential energy.

A

Ee= 0.5ke2

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20
Q

When calculating energy changes, what should mass be measured in?

A

kg

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21
Q

What are the units of energy?

A

joules

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22
Q

A woman is cycling and has a kinetic energy of 1930 J. Her mass is 94.0 kg. Calculate the velocity of the woman.

A 
1930 = 0.5 x 94 x v2
1930 = 47 x v2
1930 / 47 = v2
41.0638 = v2
√41.0638 = v
6.41 m/s = v
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23
Q

A woman is cycling and has a kinetic energy of 13800 J. Her mass is 82.6 kg. Calculate the velocity of the woman.

A 
13800 = 0.5 x 82.6 x v2
13800 = 41.3 x v2
13800 / 41.3 = v2
334.1404 = v2
√41.0638 = v
18.28 m/s
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24
Q

A woman is cycling at a velocity of 16.9 m/s and has a kinetic energy of 12300 J. Calculate the mass of the woman.

A

12300 = 0.5 x mass x 16.92
12300 = mass x 142.805
12300 / 142.805 = mass
86.1 kg = mass

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25
Q

A woman is cycling at a velocity of 9.32 m/s and has a kinetic energy of 3010 J. Calculate the mass of the woman.

A

3010 = 0.5 x mass x 9.322
3010 = mass x 43.4312
3010 / 43.312 = mass
69.3 kg = mass

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26
Q

A woman is cycling at a velocity of 16.9 m/s. The mass of the woman is 85.8 kg. Calculate the kinetic energy of the woman.

A

kinetic energy = 0.5 x 85.8 x 16.92

kinetic energy = 12252.67 J

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27
Q

A woman is cycling at a velocity of 14.8 m/s. The mass of the woman is 80.7 kg. Calculate the kinetic energy of the woman.

A

kinetic energy = 0.5 x 80.7 x 14.82

kinetic energy = 8838.26J

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28
Q

A rock of mass 0.496 kg falls from a cliff of height 6.42 m on Earth where g = 9.8 N/kg. How much gravitational potential energy did the ball lose?

A

GPE = 0.496 x 9.8 x 6.42

31.21 J

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29
Q

A rock of mass 0.991 kg falls from a cliff of height 20.0 m on Earth where g = 9.8 N/kg. How much gravitational potential energy did the ball lose?

A

GPE = 0.991 x 9.8 x 20

194.24 J

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30
Q

A rock of mass 1.99 kg falls from a cliff on Mars where g = 3.8 N/kg resulting in the rock losing 138 J of gravitational potential energy. What is the height of the cliff?

A

138 = 1.99 x 3.8 x height
138 = 7.562 x height
138 / 7.562= height
18.25 m

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31
Q

A rock of mass 1.70 kg falls from a cliff on Mars where g = 3.8 N/kg resulting in the rock losing 181 J of gravitational potential energy. What is the height of the cliff?

A

181 = 1.7 x 3.8 x height
181 = 6.46 x height
181 / 6.46 = height
28.02 m

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32
Q

A rock falls from a cliff of height 6.69 m on Pluto where g = 0.61 N/kg resulting in the rock losing 2.76 J of gravitational potential energy. What is the mass of the rock?

A
  1. 76 = mass x 0.61 x 6.69
  2. 76 = mass x 4.0809
  3. 76 / 4.0809 = mass
  4. 676 kg
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33
Q

A rock falls from a cliff of height 23.6 m on Earth where g = 9.8 N/kg resulting in the rock losing 264 J of gravitational potential energy. What is the mass of the rock?

A

264 = mass x 9.8 x 23.6
264 = mass x 231.28
264 / 231.28
1.14 kg

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34
Q

A spring has an unstretched length of 1.72 m and is stretched to a new length of 1.7712 m. The spring is now storing 0.258 J of energy. Calculate the spring constant of the spring.

A
  1. 7712 - 1.72 = 0.0512
  2. 258 = 0.5 x spring constant x 0.05122
  3. 258 = 0.00131072 x spring constant
  4. 258 / 0.00131072 = spring constant
  5. 84 N/m
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35
Q

A spring has an unstretched length of 0.286 m and is stretched to a new length of 0.678 m. The spring is now storing 4.38 J of energy. Calculate the spring constant of the spring.

A
  1. 678 - 0.286 = 0.392
  2. 38 = 0.5 x spring constant x 0.3922
  3. 38 = 0.076832 x spring constant
  4. 38 / 0.076832 = spring constant
  5. 01 N/m
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36
Q

A spring has an original length of 1.36 m and is stretched to a length of 1.655 m. Calculate the energy stored in the spring if the spring constant is 149 N/m.

A

1.655 - 1.36 = 0.295
Ee = 0.5 x 149 x 0.2952
6.48 J

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37
Q

A spring has an original length of 1.24 m and is stretched to a length of 1.986 m. Calculate the energy stored in the spring if the spring constant is 122 N/m.

A

1.986 - 1.24 = 0.746
Ee = 0.5 x 122 x 0.7462
33.95 J

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38
Q

A spring has a spring constant of 167 N/m and is stretched until it stores 14.5 J of energy. Calculate the extension of the spring.

A

14.5 = 0.5 x 167 x extension2
14.5 = 83.5 x extension2
14.5 / 83.5 = extension2
0.17365 = extension2
√0.17365 = extension
0.42 m

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39
Q

A spring has a spring constant of 156 N/m and is stretched until it stores 66.3 J of energy. Calculate the extension of the spring.

A

66.3 = 0.5 x 156 x extension2
66.3 = 78 x extension2
66.3 / 78 = extension2
0.85 = extension2
√0.85 = extension
0.92 m

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40
Q

What is the specific heat capacity of a substance. Describe in words.

A

The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree celsius

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41
Q

State the formula to calculate change in thermal energy.

A

Change in thermal energy = mass x specific heat capacity x temperature
Δ E = m c Δ θ

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42
Q

State the units for specific heat capacity.

A

J/kg °C

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43
Q

A block of metal has a mass of 1.45 kg. The block is heated and the temperature increases by 91.2 °C and the thermal energy of the block increases by 270000 J. Calculate the specific heat capacity.

A

270000 / (1.45 x 91.2) = 2041.74 J/kg°C

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44
Q

A block of metal has a mass of 0.682 kg. The block is heated and the temperature increases by 65.4 °C and the thermal energy of the block increases by 223000 J. Calculate the specific heat capacity.

A

223000 / (0.682 x 65.4) = 4999.69 J/kg°C

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45
Q

A block of metal has a mass of 2.37 kg and a specific heat capacity of 4750 J/kg°C. The block is heated up and increases in temperature by 50.0 °C. Calculate the increase in thermal energy of the metal block.

A

2.37 x 4750 x 50 = 562875 J

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46
Q

A block of metal has a mass of 0.290 kg and a specific heat capacity of 2000 J/kg°C. The block is heated up and increases in temperature by 92.2 °C. Calculate the increase in thermal energy of the metal block.

A

0.290 x 2000 x 92.2 = 53476 J

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47
Q

A block of metal has a mass of 2.64 kg and a specific heat capacity of 3170 J/kg°C. The block is heated and the thermal energy of the block increases by 684000 J. Calculate the temperature change of the metal block.

A

684000 / (2.64 x 3170) = 81.73 °C

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48
Q

A block of metal has a mass of 1.14 kg and a specific heat capacity of 3630 J/kg°C. The block is heated and the thermal energy of the block increases by 608000 J. Calculate the temperature change of the metal block.

A

608000 / (1.14 x 3630) = 146.92 °C

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49
Q

A block of metal has a specific heat capacity of 1190 J/kg°C. The block is heated and the temperature increases by 99.5 °C and the thermal energy of the block increases by 533000 J. Calculate the mass of the metal block.

A

533000 / (1190 x 99.5) = 4.51 kg

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50
Q

A block of metal has a specific heat capacity of 5640 J/kg°C. The block is heated and the temperature increases by 93.7 °C and the thermal energy of the block increases by 2010000 J. Calculate the mass of the metal block.

A

2010000 / (5640 / 93.7) = 3.80 kg

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51
Q

What are the units of energy?

A

J / joules

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52
Q

What are the units of power?

A

W / watts

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53
Q

Define power in words.

A

The rate at which energy is transferred

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54
Q

Appliance A has a power rating of 50W and appliance B has a power rating of 75W. Which appliance will transfer the most energy in 2 minutes and why?

A

Appliance B, because it ha the higher power rating.

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55
Q

State the formula that links power, time and energy transferred.

A

Power = energy transferred / time

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56
Q

State the formula that links power, time and work done.

A

Power = work done / time

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57
Q

An energy transfer of 1 joule per second is equal to how many watts>

A

1W

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58
Q

There are two motor engines that are lifting are lifting identical masses of 50kg by a height of 5m. Motor engine A lifts the mass in 5 seconds, whereas motor engine B lifts the mass in 10 seconds. Explain why in terms of the power of each motor engine. Assume both motor engines are 100% efficient.

A

Motor engine B can transfer the same amount of energy as motor engine A, but twice as fast. This means that motor engine B has a power rating that is twice as big as motor engine A.

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59
Q

A light bulb has a power of 59.6 W and is left on for 338 s. Calculate the energy used by the bulb.

A

59.6 x 338 = 20144.8J

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60
Q

A light bulb has a power of 19.2 W and is left on for 940 s. Calculate the energy used by the bulb.

A

19.2 x 940 = 18048J

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61
Q

A bulb with a power rating of 82.7 W is left on and uses 59000 J of energy. Calculate how long the bulb was on for.

A

59000 / 82.7 = 713.42s

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62
Q

A bulb with a power rating of 65.6 W is left on and uses 46200 J of energy. Calculate how long the bulb was on for.

A

46200 / 65.6 = 604.27s

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63
Q

A bulb is left on for 703 s and uses 22900 J of energy. Calculate the power of the bulb.

A

22900 / 703 = 32.57W

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64
Q

A bulb is left on for 183 s and uses 12300 J of energy. Calculate the power of the bulb.

A

12300 / 183 = 67.21W

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65
Q

Energy can be transferred usefully, stored or _______________, but cannot be _________________ or ________________.

A

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

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66
Q

What is meant by the dissipation of energy?

A

When energy is transferred to useless stores.

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67
Q

Describe the net change in energy in a closed system.

A

There is no net change in energy in a closed system.

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68
Q

When energy is dissipated it is often describe was being______________

A

Wasted

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69
Q

Describe the useful and useless energy transfers that occur when a car is used.

A

Energy is transferred from the chemical store of the battery to the kinetic energy store of the wheels - useful transfer
Energy is transferred from the chemical store of the battery to the thermal energy store of the car - useless transfer (dissipation)

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70
Q

Explain how you can reduce unwanted energy transfer between touching moving parts.

A

You can add lubrication e.g. oil
This reduces friction
Less energy transfer to useless thermal stores

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71
Q

Name the force that occurs when two objects rub together.

A

Friction

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72
Q

Explain how you can reduce unwanted energy transfers that occur when a mug of hot coffee is left in a room.

A

You can add insulation to the mug
this reduces energy transfer by heating
reduces the rate of energy transfer to thermal stores
The coffee stays warmer for longer

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73
Q

Describe the rate of energy transfer by conduction across materials that have a high thermal conductivity

A

Materials that have a high thermal conductivity have a high rate of energy transfer across them by conduction

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74
Q

Describe the rate of energy transfer by conduction across materials that have a low thermal conductivity

A

Materials that have a low thermal conductivity have a low rate of energy transfer across them by conduction

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75
Q

A builder wants to build a house. Would he decide to use a brick with a high or low thermal conductivity, why?

A

He would use a rick with a low thermal conductivity
because it has a lower rate of energy transfer by conduction across the material
So the house stays warmer for longer - lower rate of cooling

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76
Q

Building A and building B are made of the same material. The walls of building B are made up of thicker material than building A. Which building would be more suited to live in the winter and why?

A

Building B, because it is made up of more thicker material, therefore it will have a lower rate of cooling and would stay warmer for longer.

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77
Q

Describe how double-glazing windows reduce the rate of energy transfer by heating

A

They have an air gap between the two sheets of glass

this reduces energy transfer by conduction

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78
Q

Describe how draught excluders around doors and windows reduce the rate of energy transfer by heating.

A

They reduce energy transfers by convention

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79
Q

Describe how loft insulation can reduce the rate of energy transfer by heating.

A

This is foam insulation placed in the spaces in the loft

it reduces energy loss by convection

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80
Q

In which states does convection occur?

A

Liquids and gases

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81
Q

I which state does conduction occur?

A

Solids

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82
Q

A metal rod is heated at one end, explain in terms of energy and particles, how the whole rod eventually heats up.

A 
Particles gain energy and vibrate more
They collide with each other
Energy is transferred between particle's kinetic stores
the rest of the rod heats up
this is conduction
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83
Q

A container full of water is heated, explain how the whole body of water is eventually heated.

A

The heat causes some particles to gain energy
they move faster and the space between them increases
this causes the density of the region to decrease
The warmer less dense region rises over the denser cooler region
This is convection

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84
Q

A lamp is supplied with 490 J of electrical energy and has an efficiency of 27.6 %. How much energy is used usefully to emit light?

A
  1. 6/100=0.276

0. 276x490= 135.24J

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85
Q

A lamp is supplied with 369 J of electrical energy and has an efficiency of 52.0 %. How much energy is used usefully to emit light?

A 
52/100= 0.52
0.52x369= 191.88J
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86
Q

A lamp emits 178 J of useful energy as light and has an efficiency of 48.9 %. Calculate the total energy supplied to the lamp.

A 
48.9/100= 0.489
178/0.489= 364J
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87
Q

A lamp is supplied with 350 J of electrical energy and 127 J are used usefully to emit light. The rest is wasted as heat. Calculate the efficiency of the lamp.

A 
127/350= 0.362857
0.362857x100= 36.29%
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88
Q

A lamp emits 133 J of useful energy as light and has an efficiency of 32.4 %. Calculate the total energy supplied to the lamp.

A 
32.4/100= 0.324
133/0.324= 410.49J
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89
Q

A lamp is supplied with 414 J of electrical energy and 130 J are used usefully to emit light. The rest is wasted as heat. Calculate the efficiency of the lamp.

A 
130/414= 0.314
0.314x100= 31.4%
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90
Q

A lamp has a useful power output of 300W and a total power output of 450W. Calculate the efficiency of the bulb.

A

300/450=0.66666

0.6666x100= 66.67%

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91
Q

A lamp has a useful power output of 125W and a total power output of 500W. Calculate the efficiency of the bulb.

A 
125/500= 0.25
0.25x100= 25%
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92
Q

A lamp has an efficiency of 45% and a total power input of 400W, calculate the useful power output.

A 
45/100= 0.45
0.45x400= 180W
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93
Q

A lamp has an efficiency of 65% and a total power input of 750W, calculate the useful power output.

A 
65/100= 0.65
0.65x750= 487.5W
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94
Q

A lamp has an efficiency of 82% and a useful power output of 600W, calculate the total power input.

A 
0.82/100= 0.82
600/0.82= 731.70W
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95
Q

A lamp has an efficiency of 12.5% and a useful power output of 500W, calculate the total power input.

A 
12.5/100= 0.125
500/0.125= 4000W
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96
Q

State three example of fossil fuels.

A

Coal, oil and gas.

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97
Q

Are fossil fuels examples of renewable or non-renewable resources?

A

Non-renewable resources.

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98
Q

What is meant by a non-renewable resource?

A

It is being used faster than it is being made, so will eventually run out.

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99
Q

What is meant by a renewable resource?

A

It is being made as fast as it is being used. It will not run out.

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100
Q

State the three main uses of energy resources.

A

Transport, electricity generation and heating

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101
Q

State four renewable energy resources.

A

Any 4 from: Solar, win, water waves, hydro-electric, bio-fuel, tides and geothermal.

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102
Q

State two advantages of using wind turbines.

A

There is no pollution (except for a little when they are manufactured)
No fuel costs and minimal running costs.

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103
Q

State two disadvantages of using wind turbines.

A

Very noisy - noise pollution

You can’t increase supply to meet demand - they only work when it is windy.

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104
Q

State one advantages of using solar panels.

A

Can be used in remote places to power road signs and satellites.

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105
Q

State two disadvantages of using solar panels.

A

Are normally used to generate electricity on a small scale.

You can’t increase supply to meet demand - they only work when it is sunny.

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106
Q

State a disadvantage of using geothermal power.

A

There aren’t many suitable places to build the power plants. They require volcanic areas or where hot rocks like near to the surface.

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107
Q

How does hydro-electric power generate electricity?

A

A valley is flooded by building a dam. Water is then allowed to flow through turbines in the dam, generating electricity.

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108
Q

State a disadvantage of using hydro-electric power.

A

The flooding of a valley results in the loss of habitat for some species, this can lead to a reduction in biodiversity.

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109
Q

State one advantage of using hydro-electric power.

A

You can increase supply to meet demand. You allow more water to flow through the turbines.

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110
Q

How do tidal barrages work?

A

Dams are built across river estuaries with turbines in them. As the tide comes in it fills up the estuary. The water is then allowed out through the turbines at a controlled speed.

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111
Q

State one advantage of using tidal barrages.

A

They are reliable as the tides come in twice a day without fail.

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112
Q

State one disadvantage of using tidal barrages.

A

They can damage possibly result in the loss of habitat for wildlife.

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113
Q

What are bio-fuels?

A

Bio-fuels are renewable energy resources made from plant products or animal dung.

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114
Q

Describe concerns people have on using bio-fuels.

A

1) Growing crops specifically for bio-fuel might mean there is less space or water to meet the demands for crops that are grown for food.
2) Large areas of forest have been cleared to make room for bio-fuels, resulting in lots of species losing their natural habitat.

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115
Q

State three environmental problems arising from the use of fossil fuels.

A

1) Produce greenhouse gases such as carbon dioxide - contributes to global warming.
2) Can cause acid rain which can be harmful to wildlife.
3) Oil spillages can cause serious environmental problems affecting wildlife that live in the area.

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116
Q

Complete the sentence: “for electrical charge to flow through a ________ circuit, the circuit must include a source of ___________ ______________.”

A

Closed, potential, difference

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117
Q

Define current.

A

The rate of flow of electrical charge.

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118
Q

State the equation that links charge flow, current and time.

A

Charge flow = Current x time

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119
Q

What are the units of charge flow?

A

Coulomb, C

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120
Q

What are the units of current?

A

Amperes, A

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121
Q

What is the unit of time?

A

Seconds, s

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122
Q

An electrical appliance is left on for 141 s and 269 C of charge flows through it in this time. Calculate the current through the appliance.

A

269/141= 1.91A

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123
Q

An electrical appliance is left on for 15.6 s and 39.2 C of charge flows through it in this time. Calculate the current through the appliance.

A

39.2/15.6= 2.51A

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124
Q

A 3.69 A electrical appliance is left on and 875 C of charge flows through it. Calculate how long the appliance was left on for.

A

875/3.69= 237.1s

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125
Q

A 4.86 A electrical appliance is left on and 65.1 C of charge flows through it. Calculate how long the appliance was left on for.

A

65.1/4.86= 13.4s

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126
Q

A 3.41 A electrical appliance is left on for 192 s. Calculate the charge that flowed through the appliance in this time.

A

3.41x192= 654.72C

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127
Q

A 2.27 A electrical appliance is left on for 35.9 s. Calculate the charge that flowed through the appliance in this time.

A

2.27x35.9= 81.49C

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128
Q

State the equation that links voltage, current and resistance.

A

Voltage = Current x Resistance, V=IR

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129
Q

What is the unit of voltage?

A

Volts, V

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130
Q

What Is the unit of resistance?

A

Ohms, Ω

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131
Q

Voltage is also known as…

A

Potential difference

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132
Q

How should an ammeter be connected in a circuit?

A

In series.

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133
Q

What is an ammeter used to measure?

A

Amperes, A

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134
Q

What is a voltmeter used to measure?

A

Voltage, V

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135
Q

James wants to determine the voltage across a lamp. How should he connect the voltmeter?

A

He should connect the voltmeter parallel to the lamp.

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136
Q

A bulb, with a resistance of 12.4 Ω, has a current of 3.24 A passing though it. Calculate the potential difference across the bulb.

A

3.24x12.4= 40.18V

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137
Q

A bulb, with a resistance of 13.3 Ω, has a current of 4.73 A passing though it. Calculate the potential difference across the bulb.

A

4.73x13.3= 62.91V

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138
Q

A bulb has a current of 3.75 A through it, and a potential difference of 73.9 V across it. Calculate the resistance of the bulb.

A

73.9/3.75= 19.71Ω

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139
Q

A bulb has a current of 3.54 A through it, and a potential difference of 89.6 V across it. Calculate the resistance of the bulb.

A

89.6/3.54= 25.31Ω

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140
Q

A bulb, with a resistance of 11.1 Ω, has a potential difference of 25.9 V across it. Calculate the current through the bulb.

A

25.9/11.1= 2.33A

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141
Q

A bulb, with a resistance of 25.6 Ω, has a potential difference of 39.7 V across it. Calculate the current through the bulb.

A

39.7/25.6= 1.55A

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142
Q

Describe the I-V characteristic for a fixed resistor (ohmic conductor) at constant temperature

A

Current and potential difference are directly proportional, resistance is constant

143
Q

Describe the I-V characteristic of a filament lamp

A

Current and voltage are not directly proportional. Resistance is not constant, it increases as p.d. increases

144
Q

For a filament lamp, explain how resistance changes as current increases.

A

As current increases, the temperature of the filament increases, so resistance increases.

145
Q

Describe the I-V characteristic of a diode

A

The current only flows through the diode in one direction, there is a very high resistance in the reverse direction.

146
Q

A I-V relationship that shows a straight line through the origin is described as what?

A

Directly proportional.

147
Q

What does LDR stand for?

A

Light dependent resistor.

148
Q

State some of the application of LDRs.

A

Automatic night lights, outdoor lighting and burglar detectors.

149
Q

Describe how the resistance of an LDR changes with light intensity.

A

The higher the light intensity the lower the resistance.

150
Q

The resistance of a thermistor depends on what?

A

Temperature

151
Q

Describe how the resistance of a thermistor changes with temperature.

A

The higher the temperature the lower the resistance.

152
Q

State some of the applications of thermistors.

A

Car engine temperature sensors and electronic thermostats.

153
Q

When using a circuit to investigate the I-V characteristics of a component, how can the current and voltage be changed?

A

By using a variable resistor.

154
Q

If I have a voltage reading for a filament lamp, and the current reading for the circuit, how can I determine resistance?

A

Voltage / Current = Resistance

155
Q

State the two ways in which you can join electrical component in a circuit.

A

Series and parallel.

156
Q

Describe the difference in how components are set up in series compared to parallel.

A

In series the components are in one loop, in parallel each component Is connected separately to the battery in different loops by branches.

157
Q

State the rule for current in a series circuit

A

the current is the same at every point in the circuit and in every component

158
Q

State the rule for potential difference in a series circuit

A

the total potential difference of the power supply is shared between components

159
Q

State the rule for resistance in a series circuit

A

the more resistors, the greater the resistance. The total resistance is the sum of the resistance of all the components e.g. RT=R1+R2

160
Q

State the rule for current in a parallel circuit

A

Current is shared between branches. The total current is the sum of the current through all the separate components.

161
Q

State the rule for potential difference in a parallel circuit

A

the potential difference across each branch in the circuit is the same

162
Q

State the rule for resistance in a parallel circuit

A

adding more resistors in parallel decreases resistance

163
Q

Two components are connected in a series circuit with a battery. They are identical components and the battery has a pd of 10V. What share of pd will each component have?

A

5V, the pd is shared.

164
Q

Two components are connected in a parallel circuit with a battery. They are identical components and the battery has a pd of 10V. What share of pd will each component have?

A

10V

165
Q

The current in the main branch of a parallel circuit is 3A. The circuit has three identical components connected in three different branches to the battery. State the current is supplied to the each component?

A

1A, the current is shared.

166
Q

3 identical toasters are connected in a series current. The current through the first toaster is 4A, what current flows through the other two toasters?

A

4A, the current is the same everywhere.

167
Q

Four 2Ω resistors are joined in a series circuit with a battery. State the total resistance of the circuit.

A

8Ω.

168
Q

Four 2Ω resistors are joined in a parallel circuit with a battery. State the total resistance of the circuit.

A

Less than 2Ω.

169
Q

What type of supply is mains electricity?

A

AC supply.

170
Q

What do AC and DC stand for?

A

AC - alternating current

DC supply - direct current.

171
Q

State the difference between AC and DC supply.

A

In a DC supply the current flows in one direction, in an AC supply the current constantly changes direction.

172
Q

Name a component that can supply a DC supply.

A

Battery, cell.

173
Q

State the frequency of the UK’s main supply.

A

50Hz

174
Q

State the voltage of the UK’s main supply.

A

230V

175
Q

What colour is the live wire in a three core cable is…?

A

brown

176
Q

What colour is the neutral wire in a three core cable?

A

blue

177
Q

What colour is the earth wire in a three core cable?

A

green and yellow

178
Q

The brown wire in a plug is the _______ wire

A

live

179
Q

The blue wire in a plug is the ________ wire

A

neutral

180
Q

The green and yellow wire in a plug is the ________ wire

A

earth

181
Q

The potential difference between the live wire and others in the plug is _____ V

A

230V

182
Q

The potential difference between the live wire and others in the plug is _____ V

A

230V

183
Q

Current flows out of an appliance through the ______ wire

A

neutral

184
Q

The _________ wire is a safety feature of appliances

A

earth

185
Q

Potential difference between the neutral wires and others in the plug should be ____ V

A

0V

186
Q

When does the earth wire carry a current?

A

Where there is a fault in the appliance.

187
Q

Why might a live wire be dangerous even when the switch in the mains circuit is open (not closed).

A

There will be a potential difference between a person and the live wire if they touch. This will cause a current to flow through a person resulting in an electric shock.

188
Q

Why is it dangerous to provide a connection between the live wire and earth?

A

If the link creates a low resistance path to earth, a huge current will flow, which could result in a fire.

189
Q

State the equation that links power, potential difference and current.

A

Power = potential difference x current (P=VI)

190
Q

State the equation that links power, current and resistance.

A

Power = current2 x resistance

191
Q

A lamp has a power of 13500 W and a resistance of 874 Ω. Calculate the current through the lamp.

A 
13500/874 = 15.44
√15.44 = 3.93A
192
Q

A lamp has a power of 33500 W and a resistance of 362 Ω. Calculate the current through the lamp.

A 
33500/362= 92.54
√92.54= 9.62A
193
Q

A lamp has a current of 7.35 A through it and a power of 36100 W. Calculate the resistance of the lamp.

A

36100 / 7.352 = 668.24Ω

194
Q

A lamp has a current of 8.45 A through it and a power of 17800 W. Calculate the resistance of the lamp.

A

17800 / 8.452 = 249.29Ω

195
Q

A lamp has a current of 7.43 A through it and a resistance of 413 Ω. Calculate the electrical power of the lamp.

A

7.432 x 413 = 22799.62W

196
Q

A lamp has a current of 1.83 A through it and a resistance of 652 Ω. Calculate the electrical power of the lamp.

A

1.832 x 652 = 2183.48W

197
Q

A lamp has a current of 9.69 A through it and an electrical power of 93.0 W. Calculate the potential difference across the lamp.

A

93 / 9.69 = 9.60V

198
Q

A lamp has a current of 8.94 A through it and an electrical power of 86.4 W. Calculate the potential difference across the lamp.

A

86.4 / 8.94 = 9.66V

199
Q

A lamp has a potential difference of 6.03 V across it and an electrical power of 10.9 W. Calculate the current through the lamp.

A

10.9 / 6.03 = 1.81A

200
Q

A lamp has a potential difference of 6.63 V across it and an electrical power of 64.5 W. Calculate the current through the lamp.

A

64.5 / 6.63 = 9.73A

201
Q

A lamp has a current of 8.80 A through it and a potential difference of 6.03 V across it. Calculate the electrical power of the lamp.

A

6.03 x 8.80 = 53.06W

202
Q

A lamp has a current of 4.65 A through it and a potential difference of 4.00 V across it. Calculate the electrical power of the lamp.

A

4 x 4.65 = 18.6W

203
Q

Appliance A has a power of 20W and appliance B has a power of 30W. Assuming both are equally efficient, which appliance will transfer the most energy in 20 minutes and why?

A

Appliance B because it has a higher power.

204
Q

Car A and car B contain batteries that store the same amount of energy. Both cars have motors with the same efficiency. The motor of car A has a power rating of 300W, and the motor of car B has a power rating of 350W. If both cars were left running, which car would need its battery replaced first and why?

A

Car B, its motor has the highest power so a higher rate of energy transfer. Energy would be transferred from the battery quicker than the battery in car A.

205
Q

State the equation that links energy transferred, power and time.

A

energy transferred = power x time

206
Q

Energy transferred also means…

A

work done

207
Q

State the equation that links energy transferred, charge flow and potential difference.

A

energy transferred = charge flow x time

208
Q

A bulb with a power rating of 87.8 W is left on and uses 60700 J of energy. Calculate how long the bulb was on for.

A

60700 / 87.8 = 691.34s

209
Q

A bulb with a power rating of 62.4 W is left on and uses 10100 J of energy. Calculate how long the bulb was on for.

A

10100 / 62.4 = 161.85s

210
Q

A light bulb has a power of 82.7 W and is left on for 713 s. Calculate the energy used by the bulb.

A

82.7 x 713 = 58965.1J

211
Q

A light bulb has a power of 58.7 W and is left on for 915 s. Calculate the energy used by the bulb.

A

58.7 x 915 = 53710.5J

212
Q

A bulb is left on for 900 s and uses 87200 J of energy. Calculate the power of the bulb.

A

87200 / 900 = 96.8W

213
Q

A bulb is left on for 644 s and uses 8690 J of energy. Calculate the power of the bulb.

A

8690 / 644 = 13.49W

214
Q

A lamp is left on leaving 476 C of charge to flow through it whilst there is a potential difference of 122 V across the lamp. Calculate the energy transferred to the lamp.

A

476 x 122 = 58072J

215
Q

A lamp is left on leaving 187 C of charge to flow through it whilst there is a potential difference of 189 V across the lamp. Calculate the energy transferred to the lamp.

A

187 x 189 = 35343J

216
Q

A lamp is left on and 46900 J of energy are transferred to it whilst 200 C of charge flows through it. Calculate the potential difference across the lamp.

A

46900 / 200 = 234.5V

217
Q

A lamp is left on and 6780 J of energy are transferred to it whilst 23.3 C of charge flows through it. Calculate the potential difference across the lamp.

A

6780 / 23.3 = 290.99V

218
Q

A lamp is left on and 12400 J of energy are transferred to it whilst the potential difference across it is 145 V. Calculate the charge that has passed through the lamp in this time.

A

12400 / 145 = 85.52C

219
Q

A lamp is left on and 63800 J of energy are transferred to it whilst the potential difference across it is 241 V. Calculate the charge that has passed through the lamp in this time.

A

63800 / 241 = 264.73C

220
Q

What are the units of charge flow?

A

Coulomb, C

221
Q

What is the units of potential difference?

A

Voltage, V

222
Q

What are the units of power?

A

Watts, W

223
Q

Complete the sentence: “The national ____ is a system of ____________ and ________________ linking power stations to ____________________.”

A

grid, cables, transformers, consumers

224
Q

State the function of step-up transformers.

A

They are used to increase the potential difference from the power stations to the transmission cables.

225
Q

State the function of step-down transformers.

A

They are used to decrease the potential difference for domestic use.

226
Q

Why must the potential difference be lowered before electricity is transmitted into our homes?

A

So that it is at a relatively safe voltage.

227
Q

Why is the national grid an efficient way to transfer energy.

A

The national grid uses a low current and high voltage to transmit electricity at a high power. A low current means less energy is transferred to the thermal stores of the cables and lost as heat (less energy is dissipated).

228
Q

A transformer, assumed to be 100% efficient, has a potential difference of 12V and a current of 10A in its secondary coil. The current in the transformer’s primary coil is 30A. Calculate the potential difference across the transformers primary coil.

A

12 x 10 = Vp x 30
120 = Vp x 30
120/30 = Vp
4 = Vp

229
Q

State the equation that links density, volume and mass.

A

Density = mass / volume

230
Q

Why is liquid water more dense than air?

A

Liquid water has a greater number of water molecules per unit volume.

231
Q

A liquid in a beaker has a volume of 0.000110 m3and a mass of 0.157 kg. Calculate the density of the liquid.

A

0.157 / 0.000110 = 1427.27 kg/m3

232
Q

A liquid in a beaker has a volume of 0.00430 m3and a mass of 4.15 kg. Calculate the density of the liquid.

A

4.15 / 0.0043 = 965.12 kg/m3

233
Q

A liquid in a beaker has a volume of 0.00461 m3and a density of 891 kg/m3. Calculate the mass of the liquid.

A

891 x 0.00461= 4.11 kg

234
Q

A liquid in a beaker has a volume of 0.00293 m3and a density of 1330 kg/m3. Calculate the mass of the liquid.

A

1330 x 0.00293 = 3.90 kg

235
Q

A liquid in a beaker has a mass of 0.825 kg and a density of 1030 kg/m3. Calculate the volume of the liquid.

A

0.825 / 1030 = 0.0008 m3

236
Q

A liquid in a beaker has a mass of 2.02 kg and a density of 1130 kg/m3. Calculate the volume of the liquid.

A

2.02 / 1130 = 0.0018 m3

237
Q

What piece of equipment do you use to measure the mass of an irregular object?

A

A mass balance

238
Q

What piece of equipment do you use to measure the mass of an regular object?

A

A mass balance

239
Q

What piece of equipment do you use to measure the mass of a liquid?

A

A mass balance

240
Q

How can you determine the volume of a regular object?

A

Use a ruler to determine the length, width and depth. Then calculate volume by length x width x depth

241
Q

How can you determine the volume of an irregular object?

A

Fill water just below the opening of the spout of a eureka can. Place the object in the eureka can, it will displace the water. Ensure this water flows into a measuring cylinder and read of the volume.

242
Q

How can you determine the volume of a liquid.

A

Use a measuring cylinder.

243
Q

State the three states of matter.

A

Solid, liquid and gas.

244
Q

Name the process when a liquid turns into a solid.

A

Freezing.

245
Q

Name the process when a liquid turns into a gas.

A

Boiling, evaporating.

246
Q

Name the process when a gas turns into a liquid.

A

Condensation.

247
Q

Name the process then a solid turns into a liquid.

A

Melting.

248
Q

Name the process when a solid turns into a gas.

A

Sublimation.

249
Q

When the substance changes state mass is not conserved. True or false?

A

False, mass is conserved.

250
Q

Are changes of state physical or chemical changes, why?

A

They are physical changes because the substance recovers its original properties if the change is reversed.

251
Q

Define internal energy.

A

The energy stored inside a system by the particles that make up the system. Internal energy = kinetic energy + potential energy

252
Q

What is the kinetic energy of particles?

A

It is the energy related to how fast the particles are moving.

253
Q

How does heating change the energy stored in a system?

A

It increases it.

254
Q

How does cooling change the energy stored in a system?

A

It decreases it.

255
Q

Heating a substance causes one of two changes to a system, what are they?

A

Raises the temperature or causes a produces a change of state.

256
Q

What is the potential energy of particles?

A

It is the energy due to their positions.

257
Q

Which has a larger store of internal energy, 1kg of steam or 1kg of ice?

A

1kg of steam.

258
Q

Which has a lower store of internal energy, 1kg of 20oC water or 1kg of 35oc water.

A

1kg of 20oC water.

259
Q

Complete the sentence: “If the temperature of a system increases, the increase in temperature depends on the ______ of the substance heated, the type of _________________ and the _____________ input into the system.

A

mass, material, energy.

260
Q

Define specific heat capacity.

A

It is the amount of energy required to raise the temperature of 1 kilogram of a substance by 1 degree Celsius.

261
Q

A block of metal has a mass of 1.45 kg. The block is heated and the temperature increases by 91.2 °C and the thermal energy of the block increases by 270000 J. Calculate the specific heat capacity.

A

270000 / (1.45 x 91.2) = 2041.74 J/kg°C

262
Q

A block of metal has a mass of 0.682 kg. The block is heated and the temperature increases by 65.4 °C and the thermal energy of the block increases by 223000 J. Calculate the specific heat capacity.

A

223000 / (0.682 x 65.4) = 4999.69 J/kg°C

263
Q

A block of metal has a mass of 2.37 kg and a specific heat capacity of 4750 J/kg°C. The block is heated up and increases in temperature by 50.0 °C. Calculate the increase in thermal energy of the metal block.

A

2.37 x 4750 x 50 = 562875 J

264
Q

A block of metal has a mass of 0.290 kg and a specific heat capacity of 2000 J/kg°C. The block is heated up and increases in temperature by 92.2 °C. Calculate the increase in thermal energy of the metal block.

A

0.290 x 2000 x 92.2 = 53476 J

265
Q

A block of metal has a mass of 2.64 kg and a specific heat capacity of 3170 J/kg°C. The block is heated and the thermal energy of the block increases by 684000 J. Calculate the temperature change of the metal block.

A

684000 / (2.64 x 3170) = 81.73 °C

266
Q

A block of metal has a mass of 1.14 kg and a specific heat capacity of 3630 J/kg°C. The block is heated and the thermal energy of the block increases by 608000 J. Calculate the temperature change of the metal block.

A

608000 / (1.14 x 3630) = 146.92 °C

267
Q

A block of metal has a specific heat capacity of 1190 J/kg°C. The block is heated and the temperature increases by 99.5 °C and the thermal energy of the block increases by 533000 J. Calculate the mass of the metal block.

A

533000 / (1190 x 99.5) = 4.51 kg

268
Q

A block of metal has a specific heat capacity of 5640 J/kg°C. The block is heated and the temperature increases by 93.7 °C and the thermal energy of the block increases by 2010000 J. Calculate the mass of the metal block.

A

2010000 / (5640 / 93.7) = 3.80 kg

269
Q

State the units of specific heat capacity.

A

J/kgoC

270
Q

Complete the sentence: “The energy needed for a substance to change state is called_________ ________.”

A

Latent heat

271
Q

When a change of state occurs which energy store changes, kinetic or potential?

A

Potential.

272
Q

When a change in state occurs, does the internal energy of the substance change?

A

Yes.

273
Q

Define specific latent heat.

A

The amount of energy required to change the state of 1 kilogram of a substance with NO change in temperature.

274
Q

Define specific laten heat of fusion.

A

The amount of energy required to change the state from solid to liquid, of 1 kilogram of a substance with NO change in temperature.

275
Q

Define specific laten heat of vaporisation.

A

The amount of energy required to change the state from liquid to vapour, of 1 kilogram of a substance with NO change in temperature.

276
Q

State the units of specific laten heat.

A

J/kg

277
Q

On a heating graph, what do the slopes represent.

A

The substance increasing in temperature.

278
Q

On a heating graph, what do the flat sections represent.

A

The substance changing state.

279
Q

On a cooling graph, what do the slopes represent.

A

The substance increasing in temperature.

280
Q

On a cooling graph, what do the flat sections represent.

A

The substance changing state.

281
Q

A solid is heated and changes to a liquid then gas. A heating graph is drawn. State the process occurring during the first flat section.

A

Melting.

282
Q

A solid is heated and changes to a liquid then a gas. A heating graph is drawn. State the process occurring during the second flat section.

A

Boiling.

283
Q

A gas is cooled and changes to a liquid then a gas. A cooling graph is drawn. State the process occurring during the first flat section.

A

Condensation.

284
Q

A gas is cooled and changes to a liquid then a gas. A cooling graph is drawn. State the process occurring during the second flat section.

A

Freezing.

285
Q

The specific latent heat of fusion of a material is 207000 J/kg. Calculate how much energy is required to melt 3.45 kg of the material.

A

3.45 x 207000 = 714150 J

286
Q

The specific latent heat of fusion of a material is 345000 J/kg. Calculate how much energy is required to melt 0.663 kg of the material.

A

0.663 x 345000 = 228735 J

287
Q

The specific latent heat of fusion of a material is 429000 J/kg and it takes 1970000J of energy to melt a certain amount of it. Calculate the mass of the material.

A

1970000 / 429000 = 4.59 kg

288
Q

The specific latent heat of fusion of a material is 170000 J/kg and it takes 265000J of energy to melt a certain amount of it. Calculate the mass of the material.

A

265000 / 170000 = 1.56 kg

289
Q

It takes 416000 J of energy to melt 1.07 kg of a material. Calculate the specific latent heat of fusion of the material.

A

416000 / 1.07 = 388785.05 J/kg

290
Q

It takes 1460000 J of energy to melt 4.86 kg of a material. Calculate the specific latent heat of fusion of the material.

A

1460000 / 4.86 = 300411.52 J/kg

291
Q

Describe the motion of particles in a gas.

A

In constant random motion.

292
Q

What is the temperature of a gas related to?

A

The average kinetic energy of its particles.

293
Q

Describe how gas particles create pressure in a sealed container.

A

The gas particles are moving in all directions. They collide with the walls of the container exerting a force. Pressure is the force exerted per unit area.

294
Q

Do the particles in a gas all move at the same speed?

A

No, the particles in a gas move at a range of different speeds.

295
Q

Describe how increasing the temperature of a gas in a sealed container can increase the pressure.

A

Increasing temperature transfers energy to the kinetic energy store of the particles, this means particles move quicker. The particles collide more often with the walls of the container and with greater force. This increases the pressure.

296
Q

State the rough size of the radius of an atom.

A

1 x 10-10 metres

297
Q

How much smaller is the radius of a nucleus compared to the radius of an atom?

A

10000 times smaller

298
Q

What subatomic particles are present in the nucleus?

A

Protons and neutrons

299
Q

State the relative charge of a proton, neutron and electron.

A 
Proton = +1
Neutron = 0
Electron = -1
300
Q

State the relative mass of a proton neutron and electron.

A 
Proton = 1
Neutron = 1
Electron = very small
301
Q

Where can the electrons in an atom be found?

A

At different distances from the nucleus in energy levels.

302
Q

Describe how absorption of electromagnetic radiation can lead to a change in the electronic arrangement of an atom.

A

Electrons can move further from the nucleus to a higher energy level.

303
Q

Describe how emission of electromagnetic radiation can lead to a change in the electronic arrangement of an atom.

A

Electrons can move closer to the nucleus to a lower energy level

304
Q

Explain why atoms have no overall charge.

A

They contain the same amount of protons and electrons. Protons have a relative charge of +1 and electrons have a relative charge of -1. The charges cancel out.

305
Q

Complete the sentence: “All atoms of a particular element have the same number of _____________.”

A

Protons.

306
Q

What does the atomic/proton number of an element tell us?

A

The number of protons in an atom of that element.

307
Q

Define mass number.

A

The total number of protons and neutrons in an atom.

308
Q

Determine the number of protons neutrons and electrons in an atom of sodium.

A 
Protons = 11
Electrons = 11
Neutrons = 12
309
Q

Determine the number of protons neutrons and electrons in an atom of Phosphorus.

A 
Protons = 15
Electrons = 15
Neutrons = 16
310
Q

Define isotope.

A

Atoms of the same element with the same number of protons but different number of neutrons.

311
Q

Explain why Cl-35 and Cl-37 are isotopes.

A

Cl-35 has 17 protons and 18 neutrons. Cl-37 has 17 protons and 20 neutrons. They have the same number of protons but different number of neutrons.

312
Q

How do atoms turn into positive ions?

A

If they lose one or more outer electrons.

313
Q

How do atoms turn into negative ions?

A

If they gain one or more electrons.

314
Q

What did John Dalton describe atoms as?

A

Round spheres that could not be divided.

315
Q

Describe J J Thomson’s plum pudding model of the atom.

A

The atom is a ball of positive charge with negative electrons embedded in it.

316
Q

What was the name of the experiments carried out by Rutherford and Marsden?

A

Alpha particle scattering experiments

317
Q

What did Rutherford and Marsden fire alpha particles at?

A

A thin sheet of gold foil.

318
Q

What did Rutherford and Marsden observe from their experiments that surprised them?

A

Some of the alpha particles fired at the thin sheet of gold foil deflected more than expected, and a small number deflected backwards.

319
Q

What did Rutherford and Marsden conclude about the structure of the atom from their experiments?

A

That the mass of an atom was concentrated at the centre (nucleus), and that the nucleus was positively charged.

320
Q

Who adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances?

A

Niels Bohr.

321
Q

The experimental work of James Chadwick provided the evidence for which subatomic particle?

A

The neutron.

322
Q

Some atomic nuclei are unstable, how can they become stable?

A

By giving out radiation.

323
Q

Define radioactive decay.

A

A random process by which unstable nuclei release radiation to become stable.

324
Q

Define activity.

A

The rate at which a source of unstable nuclei decays.

325
Q

What is activity measured in?

A

Becquerel (Bq).

326
Q

Define count-rate.

A

The number of decays recorded each second by a detector e.g. Geiger-Muller tube.

327
Q

What is an alpha particle?

A

Two protons and two neutrons.

328
Q

What is a beta particle.

A

A high speed electron ejected from the nucleus as a neutron turns into a proton.

329
Q

What is a gamma ray?

A

A type of electromagnetic radiation.

330
Q

Describe the penetrating power of the three types of nuclear radiation.

A

Alpha particle - Low
Beta particle - Moderate
Gamma ray - High

331
Q

Describe the ionising power of the three types of nuclear radiation.

A

Alpha particle - High
Beta particle - Moderate
Gamma ray - Low

332
Q

Describe the range in air of the three types of nuclear radiation.

A

Alpha particle - Travels a few cm in air
Beta particle - Travels a few metres in air
Gamma ray - Travels long distances in air

333
Q

State the materials that can be used to stop each of the three types of nuclear radiation.

A

Alpha particle - Thin sheet of paper
Beta particle - A sheet of aluminium (roughly 5mm)
Gamma ray - Thick sheets of lead or metres of concrete

334
Q

State the symbols used for each of the three types of nuclear radiation.

A

Alpha particle - α
Beta particle - β
Gamma ray - γ

335
Q

Does the emission of gamma rays cause the mass or charge of a nucleus to change, why?

A

No, gamma rays have no mass or charge.

336
Q

An atom of Radon with mass number 219 and atomic number 86 decays to form an atom of polonium by releasing an alpha particle from its nucleus. State the mass and atomic number of the polonium atom formed.

A

Mass number: 215

Atomic number: 84

337
Q

How does the mass number change when aa nucleus releases an alpha particle?

A

Decreases by 4.

338
Q

How does the atomic number change when aa nucleus releases an alpha particle?

A

Decreases by 2.

339
Q

An atom of carbon with mass number 14 and atomic number 6 decays to form an atom of nitrogen by releasing a beta particle. State the mass and atomic number of the nitrogen atom formed.

A

Mass number: 14

Atomic number: 7

340
Q

Explain why the atomic number increases by one when a nucleus emits a beta particle.

A

When beta decay occurs, a neutron in the nucleus turns into a proton and releases a fast moving electron, so the number of protons has increased by 1.

341
Q

Complete the sentence: “Radioactive decay is a __________ process.”

A

Random.

342
Q

Define half-life.

A

The take it takes for the number of radioactive nuclei to halve.

343
Q

Do radioactive samples of different elements have the same or different half-lives?

A

They have different half-lives.

344
Q

A sample contains 200 radioactive nuclei. How many of these will decay in one half-life?

A

200/2 =100

345
Q

If the half-life of a sample is 30 seconds, how many half-lives will have occurred in 5 minutes?

A

5 x 60 = 300s

300/30 = 10 half-lives

346
Q

A sample contains 600 radioactive nuclei. The half-life is 20 seconds. How long will it take for the sample to decay to 75 radioactive nuclei?

A

600/2 = 300
300/2 = 150
150/2 = 75
3 half-lives so….. 3 x 20s = 60s

347
Q

The initial activity of a sample is 640 Bq. Calculate the final activity as a percentage of the initial activity after two half-lives.

A

1 half-life = 640 / 2 = 320
2 half-lives: 320 / 2 = 160
(160 / 640) x 100 = 25%

348
Q

A sample has a count rate of 8000 (counts/s) and falls to 1000 (counts/s) after 3 half-lives. Calculate the net decline in radioactive emissions after 3 half-lives, expressed as a fraction.

A

3 half-lives = 1/2 x 1/2 x 1/2

= 1/8

349
Q

What is radioactive contamination?

A

It is the unwanted presence of materials containing radioactive atoms on or in an object.

350
Q

What is radioactive irradiation?

A

The process of an object being exposed to nuclear radiation. The irradiated object does not become radioactive.

351
Q

What safety measures can be scientists put into place to avoid radioactive contamination?

A

They can use gloves or tongs when handling sources. They could also wear protective suits to avoid breathing in particles.

352
Q

What safety measures can be scientists put into place to avoid radioactive irradiation?

A

Keep sources in lead-lines containers. Scientists could stand behind barriers or be in different rooms and use remote-controlled arms to deal with radioactive sources.

353
Q

Explain why irradiation is a concern when radioactive sources emit beta and gamma radiation instead of than alpha particles.

A

Outside the body beta and gamma sources are most dangerous because they can penetrate the skin, alpha particles can’t. So high levels of irradiation from sources that emit beta and gamma radiation are particularly dangerous.

354
Q

Explain why contamination is a serious concern when radioactive sources emit alpha radiation instead of than beta and gamma radiation.

A

Inside the body alpha sources are more dangerous, because they do all their damage in a localised area. They have the highest ionising power. They also cannot pass through the skin. Whereas beta and gamma radiation can pass through the skin and are less ionising.

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