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Physics > Heat and Temperature (And 6th year Magnetism): > Flashcards

Heat and Temperature (And 6th year Magnetism): Flashcards

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1
Q

temperature

A

the measure of the hotness or coldness of a body

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2
Q

SI unit for temperature

A

the kelvin K

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3
Q

for practical work

A

ºC

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4
Q

ºC =

A

K - 273.15

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5
Q

Δθ = 5ºC =

A

5K

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6
Q

thermometric property

A

the physical property of a thermometer that changes measurable with temperature

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7
Q

4 thermometric properties

A

length of a column of mercury
emf of a thermocouple
resistance of a wire
colour of liquid crystals

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8
Q

what is the standard thermometer

A

the laboratory mercury thermometer

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9
Q

to calibrate a liquid in glass thermometer experiment

calibration graph, y axis

A

length cm

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10
Q

to calibrate a thermometer experiment

calibration graph, x axis

A

temperature ºC

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11
Q

to calibrate a liquid in glass thermometer

2 points on accuracy

A
  1. use a stirrer to ensure water has uniform temperature

2. avoid error of parallax when using the half metre stick to measure the length of the liquid in a glass tube

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12
Q

calibrating a thermocouple thermometer y-axis

A

emf (mV)

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13
Q

what do you place in the substance you want to check temperature of with thermocouple thermometer

A

hot junction

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14
Q

reference junction

A

cold junction

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15
Q

how to find temperature of reference junction

A

finding the value of the point of intersection of the graph and the x-axis

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16
Q

2 different thermometers

A

don’t agree

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17
Q

the values of different thermometers

A

will most likely not be the same

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18
Q

why do the 2 values not agree?

A

different thermometers based on different thermometric properties respond in a different way to a given rise in temperature giving somewhat different values

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19
Q

is there a correct thermometer?

A

we choose a standard thermometer against which all other thermometers can be compared

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20
Q

what is special about a clinical thermometer?

A

there is a constriction

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21
Q

what is the constriction in the medical thermometer designed to do?

A

designed to stop the liquid from falling back into the reservoir when the thermometer is taken out of the patient’s mouth

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22
Q

how is the liquid in the medical thermometer got back into the reservoir

A

it is shaken before used on next patient

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23
Q

2 uses of a thermocouple thermometer

A

in an oven or a boiler

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24
Q

how is the thermocouple thermometer read?

A

the emf generated would be translated to a temperature reading

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25
Q

what flows between hotter and cooler substance?

A

heat energy

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26
Q

atoms in hot and cold substances moving in

A

moving in a 3 dimensional type of vibration

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27
Q

atoms in hot and cold substances have what energy

A

kinetic and potential energy

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28
Q

energy inside hot and cold substances

A

internal energy

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29
Q

which substance has more internal energy

A

the hotter substance

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30
Q

why does the hotter substance have more internal energy?

A

the kinetic energy is greater due to vibrations in the hotter substance

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31
Q

what is heat?

A

the form of energy transferred from the hotter substance to the cooler substance as a result of the temperature difference between them

32
Q

definition of heat capacity

A

the heat energy needed to change the temperature of an object by 1K

33
Q

symbol of heat capacity

A

C

34
Q

unit of heat capacity

A

JK -1

35
Q

definition of specific heat capacity

A

the heat energy needed to change the temperature of 1 Kg of the object by 1 K

36
Q

symbol of specific heat capacity

A

c

37
Q

unit of specific heat capacity

A

J Kg -1 K-1

38
Q

energy needed to change temperature formula

A

mcΔθ

39
Q

m

A

mass of substance

40
Q

c

A

specific heat capacity

41
Q

Δθ

A

temperature change

42
Q

energy needed to change temperature =

A

kinetic energy (1/2 m v squared )

43
Q

to measure specific heat capacity by an electrical method. what do you do before the experiment?

A

let the arrangement stand for several minutes before the electricity is switched on

44
Q

to measure specific heat capacity by an electrical method. why do you let it stand for a few minutes

A

to ensure that t he temperature of the liquid equals the temperature of the calorimeter

45
Q

to measure specific heat capacity by an electrical method. 4 steps in the experiment

A
  1. record the mass of the calorimeter and mass of the liquid
  2. record the initial temperature of the liquid and calorimeter
  3. allow current to flow for 5 minutes, record electrical energy supplied by using the joulemeter
  4. record the final temperature of the liquid and calorimeter
46
Q

to measure specific heat capacity by an electrical method. electrical energy supplied =

A

heat energy gain + heat energy gain of calorimeter

47
Q

to measure specific heat capacity by an electrical method. 2 points on accuracy

A
  • avoid small rise in temperature as measuring small values results in greater percentage errors
  • use a sensitive thermometer to get a precise value of the temperature rise
48
Q

what do storage heaters contain?

A

concrete blocks with a large value of specific heat capacity

49
Q

when do storage heaters heat up and why?

A

heat up at night when the demand for electricity is less and is cheaper

50
Q

why do storage heaters absorb large amounts of heat?

A

because of the large heat capacity

51
Q

what do storage heaters do during the day?

A

they cool down by releasing their heat to the surrounding air

52
Q

water can

A

absorb large amounts of heat

53
Q

very useful liquid in radiators

A

water

54
Q

to measure specific heat capacity by a mechanical method what do you do before the experiment

A

let sit for several minutes before copper is added

55
Q

to measure specific heat capacity by a mechanical method what do you do before the experiment, why do you let sit for several minutes before copper is added?

A

ensures that the temperature of the liquid equals the temperature of the calorimeter

56
Q

heat loss of hot copper =

A

heat energy gain of liquid + heat energy gain of calorimeter

57
Q

what is the calorimeter usually made of?

A

copper

58
Q

water at 100º and water at 20º added, heat change of hotter one

A

100º - x

59
Q

water at 100º and water at 20º added, heat change of cooler one

A

x-20º

60
Q

when calculating the moment of a force causing something to move in a circle, what is the perpendicular distance?

A

the radius

61
Q

moment of a force causing something to move in a circle

A

IlB x radius

62
Q

moment of a couple causing something to move in a circle

A

IlB x diameter

63
Q

magnetic flux formula

A

Φ = BA

64
Q

Φ

A

magnetic flux

65
Q

B

A

magnetic flux density

66
Q

A

A

area through which magnetic flux density is acting

67
Q

unit of magnetic flux

A

tesla x m2

68
Q

Faraday’s law - ENGLISH

A

if the magnetic flux lines passing through a circuit change, then an emf is induced
the induced emf is proportional to the rate of change of magnetic flux passing through the circuit

69
Q

Faraday’s law - MATHS

A

emf ∝ dΦ/dt
emf = -N dΦ/dt
(N= number of turns in coil)
(ignore negative in maths equation)

70
Q

Lenz’s law - ENGLISH

A

The induced emf makes a current flow in such a direction as to oppose the change that caused it

71
Q

ac Resultant voltage =

A

source voltage - induced voltage

72
Q

ac if the frequency of the a.c source is increased

A

the induced voltage is greater and the resultant voltage is smaller, bulb is less bright

73
Q

ac if an iron core is inserted into a solenoid

A

magnetic flux is stronger, greater induced voltage, decrease in resultant voltage, less bright bulb

74
Q

dc initially

A

current flows in the same direction, magnetic field is constant, no emf???

75
Q

dc maximum brightness

A

takes time for maximum brightness to be reached

76
Q

dc increase briefly induced emf 2

A

more turns of a wire of the solenoid

insert an iron core into the solenoid

77
Q

dc if the switch is opened

A

self induction happens for a brief time interval, small delay in the bulb’s brightness reducing to zero

Physics (11 decks)

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