Topic 1 Flashcards

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1
Q

Define physical quantity

A

A quantity that can be measured and consists of a magnitude and a unit

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2
Q

What are SI units?

A

The International System of Units

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3
Q

Name the 6 SI units

A
  • Metre
  • Kilogram
  • Second
  • Ampere
  • Kelvin
  • Mole
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4
Q

Define base quantity

A

Quantities on the basis of which other quantities are expresses

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5
Q

Define derived quantities

A

Quantities that are expressed in terms of base quantities

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6
Q

Define homogenuous

A

Quantities on both sides of an equation have the same unit

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7
Q

Homogeneous equation may not be ______ correct but a _______ correct equation is definitely homogeneous

A

Physically

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8
Q

What are the 9 prefixes, their abbreviations and powers

A

nano n 10^-9
micro μ 10^-6
milli m 10^-3
centi c 10^-2
deci d 10^-1
kilo k 10^3
mega M 10^6
giga G 10^9
tera T 10^12

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9
Q

Define scalar quantity

A

Quantities that have magnitude only and no direction

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10
Q

Define vector quantity

A

Quantities that have both magnitude and direction

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11
Q

Give 7 examples of a scalar quantity

A

Mass, temperature, energy, distance, speed, density, pressure

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12
Q

Give 6 examples of a vector quantity

A

Displacement, velocity, weight, acceleration, force, momentum

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13
Q

What is the difference between collinear and coplanar?

A

Collinear is parallel to the same line and coplanar is parallel to the same plane

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14
Q

Define uncertainty

A

Estimate of the difference between the reading and the true value of the quantity

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15
Q

Define error

A

A reason that a measurement might be wrong

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16
Q

Define precision

A

The smallest change in a value that can be measured by an instrument or an operator. To be precise, repeated measurements of the same thing should be close

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17
Q

Define accuracy

A

An accurate value of a a measured quantity is one that is close to the true value of the quantity

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18
Q

What is a systematic error?

A

A factor that causes readings to be different form the true value by a consistent amount each time the reading is made

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19
Q

What is a zero error?

A

A type of systematic error which occurs when an instrument gives a non-zero reading when the true value of the quantity is 0

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20
Q

How can you get rid of a zero error?

A

Can be removed by adding or subtracting it from your values

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21
Q

What is a random error?

A

Causes readings to vary around the mean value in an unpredictable way from one reading to another

22
Q

How can a random error be reduced?

A

By repeating and averaging results

23
Q

How do you find the uncertainty of a single measurement?

A

Precision of the measurement device (smallest value measured by the device)

24
Q

How do you find the uncertainty of repeated measurements?

A

Half the range of the measured values

25
Q

How do you find the uncertainty of repeated IDENTICAL measurements?

A

Precision of the measurement device

26
Q

State the formula for percentage uncertainty

A

Uncertainty
———————– x 100 (1 s.f.)
Measured value

27
Q

How to combine uncertainties when adding or subtracting?

A

Add the absolute uncertainties

28
Q

How to combine uncertainties when multiplying?

A

Add the percentage uncertainties

29
Q

How to combine uncertainties when raising to a power?

A

Multiplying the percentage uncertainties by the power

30
Q

Is parallax error systematic or random?

A

Systematic if you always view the dial from the same angle and random if you view the dial from a random angle each time

31
Q

Is reaction error systematic or random?

A

Random error (Reaction time can vary)

32
Q

Do random errors or systematic errors affect the average?

A

Only systematic affect the average (bias) and random only affects the variability around the average

33
Q

What are the sources of random errors? (2)

A
  • Operator systems
  • Changes in experimental conditions
34
Q

Define limit of reading

A

The smallest graduation of the scale of an instrument

35
Q

What are the sources of systematic errors? (3)

A
  • Instrumental
  • Physical
  • Human limitation (device is out of callibration)
36
Q

How to minimise systematic errors? (2)

A
  • Careful calibration
  • Best possible techniques
37
Q

What is precision affected by and what does it look like on a graph?

A

Random error
Scattering about straight line

38
Q

What is accuracy affected by and what does it look like on a graph?

A

Systematic error
Straight line parallel to best fit

39
Q

What is an oscilloscope?

A

A test instrument that allows you to look at the ‘shape’ of electrical signals by displaying a graph of voltage against time

40
Q

What can the graph on an oscilloscope also be called?

A

Trace

41
Q

How is a graph from an oscilloscope drawn?

A

By a beam of electrons striking the phosphor coating of the screen, making it emit light (green/blue)
- like how a tv picture is produced

42
Q

How does an oscilloscope work?

A

They contain a vacuum tube with a cathode at one end to emit electrons and an anode to accelerate them so they move rapidly down the tube to the screen

43
Q

What are the cathode and the anode in an oscilloscope also called?

A

Electron gun

44
Q

What is the purpose of the deflection plates in an oscilloscope?

A

They deflect the electron beam up/down and left/right

45
Q

What can the electrons in an oscilloscope also be called?

A

Cathode rays

46
Q

How do you obtain a clear and stable trace on an oscilloscope?

A

Adjust the controls
- Y amplifier (volts/cm) to determine the height of the trace
- Timebase (time/cm) to determine the rate at which the dot sweeps the screen

47
Q

What is the amplitude?

A

The maximum voltage reached by the signal

48
Q

What is the peak-peak voltage?

A

2 times the amplitude

49
Q

What is the time period?

A

The time taken for the signal to complete one cycle

50
Q

What is the frequency?

A

Number of cycles per second
OR 1/Time period

51
Q

Why is the peak-peak voltage read?

A

It can be read correctly even if the position of 0v is not known