Topic 1 Flashcards

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1
Q

What are the base units?

A

mass (kg)

length (m)

time (s)

current (A)

temperature (K)

amount of substance (mol)

luminous intensity (cd)

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2
Q

What happens to uncertainty when adding values?

A

Add the absolute uncertainties.

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3
Q

What happens to uncertainty when subtracting values?

A

Add the absolute uncertainties.

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4
Q

What happens to uncertainty when multiplying values?

A

Add the percentage uncertainties.

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5
Q

What happens to uncertainty when dividing values?

A

Add the percentage uncertainties.

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6
Q

What happens to uncertainty when taking powers of values?

A

Multiply the percentage uncertainty by the power.

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7
Q

How to find the absolute uncertainty

A

± half of the smallest division of the measuring instrument.

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8
Q

What happens to uncertainty if you are taking a measurement between two readings?

A

± half of smallest division of measuring instrument (x2)

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9
Q

How do you reduce uncertainty?

A

1) Take multiple instances of the same value (eg the time taken for 10 oscillations).
2) Take repeated measurements.

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10
Q

What are systematic errors?

A

Errors which occur every time you repeat an experiment, meaning results differ from the true reading by a constant amount each time.

They affect accuracy but not precision.

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11
Q

What are random errors?

A

Errors cause results to vary in an unpredictable way, meaning readings are spread around the true value.

They affect accuracy as well as precision.

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12
Q

When do systematic errors occur?

A

When using faulty equipment or due to the environment.

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13
Q

When do random errors occur?

A

When control variables are not kept the same throughout the experiment.

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14
Q

Definition: True value

A

The exact value which would be obtained in an ideal measurement.

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15
Q

Definition: Accuracy

A

The closeness of results to the true value.

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16
Q

Definition: Precision

A

The closeness of results to each other.

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17
Q

Definition: Resolution

A

The smallest change that can be registered by the measuring instrument.

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18
Q

Determine the acceleration of a freely-falling object: Set up

A
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19
Q

Determine the acceleration of a freely-falling object: Method

A

1) Drop the ball bearing through light gates (or) use an electro magnet with a switch and a trap door switch to measure the time taken for a ball bearing to fall a certain distance.
2) Repeat the measurements to find an average.
3) Measure and record the height fallen by the object.

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20
Q

Determine the acceleration of a freely-falling object: Safety

A
  • Ensure the apparatus is stable as it might topple over.
  • Be aware of falling ball bearing on feet.
  • Turn off electromagnet when not in use to prevent over-heating.
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21
Q

Determine the acceleration of a freely-falling object: Improvements

A

• Use light gates (or) trap door switches to calculate the time taken for the ball to fall in order to reduce the effect of human reaction times.

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22
Q

Determine the electrical resistivity of a material: Set up

A
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23
Q

Determine the electrical resistivity of a material: Method

A

1) Set up a length of wire along side a metre ruler.
2) Attach a crocodile clip at the zero end of the meter ruler.
3) Use the second crocodile clip to attach to the wire at different locations.
4) At each location, measure the resistance and the length of the wire.
5) Measure the diameter of the wire.

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24
Q

Determine the electrical resistivity of a material: Safety

A
  • Currents are small so present no hazard.
  • Disconnect wires between readings to prevent over-heating.
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25
Q

Determine the electrical resistivity of a material: Improvements

A
  • Measure the diameter of wire at different locations and find an average.
  • Take measurements at regular intervals to get a good spread of data.
  • Use a voltmeter and ammeter which read to more significant figures.
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26
Q

Determine the emf and internal resistance of an electrical cell: Set up

A
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27
Q

Determine the emf and internal resistance of an electrical cell: Method

A

1) Connect the cell (with internal resistance), ammeter and variable resistor in series, with the voltmeter parallel to the variable resistor.
2) Vary the resistance of the variable resistor and record values for V and I.
3) Repeat these measurements at different resistances.

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28
Q

Determine the emf and internal resistance of an electrical cell: Safety

A
  • Be careful not to short circuit the circuit.
  • Handle meters with care so not to damage.
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29
Q

Determine the emf and internal resistance of an electrical cell: Improvements

A

• Use voltmeters and ammeters which read to more significant figures.

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30
Q

Use a falling-ball method to determine the viscosity of a liquid: Set up

A
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31
Q

Use a falling-ball method to determine the viscosity of a liquid: Method

A

1) Weigh all of the balls, and measure their radius to calculate the density of the balls.
2) Place one rubber band around the top of the tube, and one around the bottom of the tube.
3) Drop the balls one by one into the tube, and measure the time for each one to fall from the top band to the bottom band.
4) Repeat with each ball to find an average.

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32
Q

Use a falling-ball method to determine the viscosity of a liquid: Safety

A
  • Clear up washing up liquid immediately to prevent spillage.
  • Wear goggles so that washing up liquid doesn’t come into contact with eyes.
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33
Q

Use a falling-ball method to determine the viscosity of a liquid: Improvements

A
  • Make sure the top rubber band is low enough to allow the ball to reach terminal velocity before it passes through.
  • Measure the diameter of the balls at different points to find an average.
34
Q

Determine the Young modulus of a material: Set up

A
35
Q

Determine the Young modulus of a material: Method

A

1) Measure the diameter of the wire and the length of the wire from the wood blocks to the edge of the paper.
2) Add masses to the hanger and record the position of the marker against the metre ruler.
3) Calculate the extension for each mass added.
4) Repeat each time you add a mass.

36
Q

Determine the Young modulus of a material: Safety

A
  • The wire will be under tension and may break so giggles should be worn.
  • Masses could fall into your feet.
37
Q

Determine the Young modulus of a material: Improvements

A
  • Use a long wire so that the extension is large enough to read.
  • Measure the diameter of the wire at different locations and find an average.
38
Q

Determine the speed of sound in air: Set up

A
39
Q

Determine the speed of sound in air: Method

A

1) Set up a microphone connected to a signal generator and oscilloscope next to a speaker.
2) Move the microphone away from the speaker slowly until the first maximum amplitude is heard and record the distance.
3) Then, continue to move the microphone further away to the next maximum amplitude and record the distance.
4) Repeat this process and find the average distance between adjacent maximums.

40
Q

Determine the speed of sound in air: Safety

A
  • Ensure the sound isn’t too loud to cause any damage.
  • Take precaution with use of mains electricity.
41
Q

Determine the speed of sound in air: Improvements

A
  • Record the distance of minimums instead as it is easier to detect when the amplitude is zero.
  • Repeat the practical to find an average.
42
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string: Set up

A
43
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string: Method

A

1) Attach to one end of the string a vibration transducer and pass the other end over a pulley with a mass hanger.
2) Add masses and turn on the signal generator to oscillate the string.
3) Change the frequency of the signal generator until a standing wave is produced of the fundamental node of maximum amplitude.
4) Record the frequency’s
5) Repeat the investigation with different factors.

44
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string: Safety

A
  • String could break and weights fall on feet.
  • Wear giggles to prevent string hitting eye in case of a break.
45
Q

Investigate the effects of length, tension and mass per unit length on the frequency of a vibrating string: Improvements

A
  • Use rubber instead of metal to prevent the risk of a breakage.
  • Take repeats or ask for someone else’s opinion on when maximum amplitude is observed.
46
Q

Determine the wavelength of light from a laser using a diffraction grating: Set up

A
47
Q

Determine the wavelength of light from a laser using a diffraction grating: Method

A

1) Pass a laser beam through a diffraction grating.
2) Measure the distance between the grating and the wall.
3) Measure the distance between the zero order maximum and the first order maximum.
4) Measure the distance for increasing orders .
5) Repeat with a different diffraction grating which has a different number of slits.

48
Q

Determine the wavelength of light from a laser using a diffraction grating: Safety

A
  • Lasers should have a small power output to prevent damage to eyes.
  • Don’t shine laser into eyes.
49
Q

Determine the wavelength of light from a laser using a diffraction grating: Improvements

A

• Use a laser light as it is monochromatic and so the maximum is small.

50
Q

Investigating the relationship between the force exerted on an object and its change of momentum: Set up

A
51
Q

Investigating the relationship between the force exerted on an object and its change of momentum: Method

A

1) Place a piece of card on a glider which is placed onto an air slide.
2) Attach the glider to a piece of string which will hang over a pulley with weights attached.
3) Release the slider and record the time taken for the card to pass through the light gate.
4) Measure the length of the card to allow you to calculate the speed.
5) Repeat with different weights attached.

52
Q

Investigating the relationship between the force exerted on an object and its change of momentum: Safety

A
  • Place a shock pad underneath the weights to prevent damage in case they hit the floor.
  • Do not Place your feet under the weights in case of a breakage.
53
Q

Investigating the relationship between the force exerted on an object and its change of momentum: Improvements

A
  • Release the slider from the same place each time.
  • Use the same slider to avoid friction differences.
54
Q

Use ICT to analyse collisions between small spheres: Set up

A
55
Q

Use ICT to analyse collisions between small spheres: Method

A

1) Measure the mass and diameter of both spheres.
2) Set up a digital to record a collision between the two spheres which is to take place on a drawing board to help reference.
3) Roll one sphere into a second stationary one.
4) Use software to analyse the video clips to measure velocity etc.
5) Repeat.

56
Q

Use ICT to analyse collisions between small spheres: Safety

A

• Be careful with the balls falling off table, but risk is very low.

57
Q

Use ICT to analyse collisions between small spheres: Improvements

A
  • Use a grid underneath the balls to help reference the positions of the balls during the collision.
  • Practice before until you are confident with making the collisions.
58
Q

Analysing the pd across a capacitor as it charges: Set up

A
59
Q

Analysing the pd across a capacitor as it charges: Method

A

1) Use a multimeter to measure the value of the resistor and an oscilloscope to measure the emf.
2) Flick the switch or flying lead so that the capacitor charges up.
3) Measure the pd across the capacitor at different times using a data logger.
4) Repeat.

60
Q

Analysing the pd across a capacitor as it charges: Safety

A
  • Use low currents to prevent heating of wires.
  • Do not exceed voltage rating of the capacitor.
61
Q

Analysing the pd across a capacitor as it charges: Improvements

A

• Use a series circuit so the capacitor charges up through the resistor.

62
Q

Calibrating a thermistor as a thermostat: Set up

A
63
Q

Calibrating a thermistor as a thermostat: Method

A

1) Add boiling water (at 100 degrees) to a beaker containing the thermistor.
2) Make recordings of the temperature and the corresponding resistance across the thermistor.
3) Draw a graph of output voltage against temperature.
4) Determine the temperature at which the thermistor should turn off, and find the corresponding resistance value.

64
Q

Calibrating a thermistor as a thermostat: Safety

A
  • Do not exceed the voltage rating of the thermistor as this may lead to a fire.
  • Secure the beaker so that it does not topple.
65
Q

Calibrating a thermistor as a thermostat: Improvements

A
  • Heat slowly to allow thermal equilibrium to occur.
  • Use a datalogger to record your results.
66
Q

Determine the Specific latent heat of ice: Set up

A
67
Q

Determine the Specific latent heat of ice: Method

A

1) Place ice in funnel and allow it to warm up to 0 degrees.
2) Determine the mass of the empty beaker, before adding 100 cm3 of water to the beaker and measuring again.
3) Measure the temperature of the water before adding ice to the beaker and stirring until the ice melts.
4) Measure the mass of the beaker once again now it contains ice before recording the lowest temperature reached by the ice water.

68
Q

Determine the Specific latent heat of ice: Safety

A
  • Be careful not to topple over the boiling water.
  • Mop up any spillages immediately to prevent slip hazards.
69
Q

Determine the Specific latent heat of ice: Improvements

A
  • Allow time for thermal equilibrium to occur.
  • Insulate the block to prevent heat transfer to or from the surroundings.
70
Q

Investigate the pressure and volume of a gas at fixed temperatures: Set Up

A
71
Q

Investigate the pressure and volume of a gas at fixed temperatures: Method

A

1) Slowly compress the pump to different levels.
2) Record the length of air column and pressure at each level.
3) Repeat.

72
Q

Investigate the pressure and volume of a gas at fixed temperatures: Safety

A
  • Wear safety goggles in case the tubing breaks.
  • Apply a weight to the apparatus to prevent it from falling over.
73
Q

Investigate the pressure and volume of a gas at fixed temperatures: Improvements

A
  • Compress the gas slowly to keep the temperature constant so that the velocities of the gas molecules don’t change.
  • This would effect the pressure of the gas.
74
Q

Investigate the absorption of radiation by lead: Set up

A
75
Q

Investigate the absorption of radiation by lead: Method

A

1) Determine the background rate using the GM tube and counter without the source.
2) Measure the thickness of each of the lead absorbers.
3) Set up the equipment with the GM tube pointing towards the source.
4) Record the count rate for each of the different thicknesses of lead absorbers.
5) Subtract the background count rate from the recorded count rate to get the corrected count rate.

76
Q

Investigate the absorption of radiation by lead: Safety

A
  • Keep a fat distance from the source and do not touch it.
  • Put away the source when not in use.
  • Do not point the source at you.
  • Wash hands after use.
77
Q

Investigate the absorption of radiation by lead: Improvements

A
  • Repeat the recordings as decay is random.
  • This will allow you to take an average and find the uncertainty in your values.
78
Q

Determine the value of an unknown mass using oscillations: Set up

A
79
Q

Determine the value of an unknown mass using oscillations: Method

A

1) Set the oscillator going and measure the time for it to complete a number of oscillations.
2) Count the number of oscillations and record the time taken for these oscillations to occur.
3) Calculate the average time for one of these oscillations to occur.
4) Repeat.

80
Q

Determine the value of an unknown mass using oscillations: Safety

A
  • Do not overload the spring so that it breaks when oscillating.
  • Weight the support stamp to prevent it from falling over.
81
Q

Determine the value of an unknown mass using oscillations: Improvements

A
  • Do not overload the spring so that it doesn’t exceed elastic limit.
  • Record the time over many oscillations and divide by the number of oscillations, to reduce uncertainty.