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GEN0005 (Engineering Principles) > Week 2 > Flashcards

Week 2 Flashcards

1
Q

What is Heat?

A

Form of energy measured in Joules (J)

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2
Q

The principle of Energy conversation?

A

Energy can not be created or destroyed

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3
Q

What is energy efficiency?

A

The proportion of energy which comes out in the form we want
is called the efficiency

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4
Q

What are the 3 modes of heat transfer?

A

-Conduction
-Convention
-Radiation

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5
Q

What is conduction?

A

Heat transfers through a body.
Molecules at high temperature vibrate more than those at lower
temperature. If they collide, some energy is passed from the hot one to the
cooler one, and so energy moves through the material.

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6
Q

What is convection?

A

Molecules of a fluid (liquid or gas) move from
place to place, carrying heat with them.

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7
Q

What is free convection?

A

As the fluid heats up it becomes less dense and rise, cooler fluids move in to take its place

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8
Q

What is forced convection?

A

Fluid is transferred from place to place by a pump or a fan.

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9
Q

What is radiation?

A

Heat travels through free space. This is the only way
energy can be transferred through a vacuum.

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10
Q

Why would we want to insulate stuff?

A

-To keep things hot or cool
-To stop heat from affecting the surrounding areas
-To avoid wasting heat

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11
Q

How do we prevent conduction?

A

We use an insulator (A poor thermal conductor) like plastics, fibres, gases

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12
Q

How to prevent convection?

A

We need to remove the fluid moving, by confining it in a small space
-Fabrics, foam, and wet suits, stop heat flowing away from body
-Vacuum flask and double glazing actually remove the fluid to prevent convection

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13
Q

How to prevent radiation?

A

We make the surface reflective so that any energy arriving from inside is reflective back in or from the outside reflective back out

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14
Q

What is Heat Capacity?

A

Heat Capacity of the body is defined as “The amount
of heat required to increase the temperature of the
body by 1 K (or 1°C)” and is given a symbol as C.

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15
Q

What is the formula of heat capacity?

A

Heat Capacity (C)= Change in Q)/Change in T

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16
Q

What does change in Q mean?

A

The amount of heat required (In Joules) to produce a change in temperature

17
Q

What is the unit of heat capacity?

A

JK^-1

18
Q

What is a constant in specific heat capacity?

A

C/m as the heat capacity will be proportional to the mass of the bdoy

19
Q

What is C/m?

A

Specific heat capacity

20
Q

What is specific heat capacity?

A

“The amount of heat required to increase the temperature of 1 kg of
the substance by 1 K (or 1°C)”

21
Q

What is the formula of Specfic heat capacity?

A

Change in Q=m c x change in temperature

22
Q

What is the equation of Power?

A

Power=Change in 1/ Time

23
Q

What is the formula for change in Q?

A

Change in Q= m c x delta t

24
Q

What is specific heat capacity measured in?

A

J (Joules)

25
Q

What is the difference between heat capacity and specific heat capacity?

A

Heat Capacity C is a property of the body as a whole. Different parts of it may be made from different materials
Specific Heat (Capacity) c is a property of the material.

26
Q

What is the unit of Power?

A

W

27
Q

What is the Coefficient of Thermal Conductivity?

A

A material property representing how well the material conducts heat. The
heat conduction equation with definitions would also be an acceptable
answer

28
Q

How to get specific heat capacity in a liquid experiment?

A

Equipment needed
- Switch and power supply
-Thermometer
-Lagging Jacket (Used for preventing heat loss)
-Electric Heater
-Test Specimen

During the experiment
-Record the power (P=IV)
-Measure Initial temperature and final temperature
-Calculate Q=IVt
-Calculate Specific Heat Capacity (Q=mc(T2-T1=Q/m(T2-T1)

29
Q

How to convert from Celsius to Fahrenheit?

A

+273.5

30
Q

All formulas for Q (Energy)

A

-Q=Pt (Energy=Power x Time)
–Q=IVt (Energy= CurrentxVoltagexTime)
-Q=mc(T2-T1) (Energy=mass x specific heat capacity x Change In temperature)

31
Q

What is the final heat balance equation and explain it?

A

Q(Main Component)+Q(1st Medium)+Q(2nd Medium) =0

-There is no heat change in an insulated system based on the laws of conversation o energy
-Hotter Objects experience Heat Loss and Cooler objects experience Heat Gain

32
Q

If there is heat loss in a system how do we calculate total Energy?

A

You add heat loss to Q-IVt

33
Q

Formula for heat capacity

A

C=Change in Q/Change in T (Change in energy/change in temperature)

34
Q

What is the reationship of

A

GEN0005 (Engineering Principles) (5 decks)

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