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Physics > Energy > Flashcards

Energy Flashcards

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1
Q

What is efficiency

A

Useful energy transferred by a device devided by total energy supplied

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2
Q

What is a system

A

An object or group of objects, for example an apple sitting on a table is a system

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3
Q

What does defining a system help doing

A

It helps focus only on what is relevant to the situation being observed

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4
Q

What happens when a system is an equillibirum

A

Nothing happens so nothing chnages

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5
Q

What is the meaning of equilibrium

A

A state where opposing forces are balanced

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6
Q

What is energy measured in

A

Joules (J)

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7
Q

What is a thermodynamic system

A

A system not limited from the surroundings by real of fake boundaries

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8
Q

What does an open system allow to happen

A

Allows the exchange of energy and matter to or from its surroundings

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9
Q

What does a closed system allow to happen

A

Allows the exchange of energy but not matter to or from its surroundings

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10
Q

What does an isolated system not allow happen

A

Does not allow the transfer of matter or energy to or from its surroundings

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11
Q

Describe the energy transfer when an object is thrown up

A

. The person holding the ball has energy in the chemical store
. When the ball is thrown, energy is transferred to the kenetic store
. When the ball is moving energy is transferred to gravitational/ potential store

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12
Q

Describe the energy transfer in a boiling kettle

A

When water is being boiled energy from the electricsl working store is transferred to the thermal store

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13
Q

What is kinetic energy

A

Kinetic energy is the energy of motion

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14
Q

How csn kinetic energy be calculated

A

Kenetic Energy (J) = 1/2 x m x v^2

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15
Q

What is gravitational potential energy

A

The energy of an object has due to its height in a gravitational field

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16
Q

How can gravitational energy be calculated

A

Gravitational potential energy (J)= m x g x h

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17
Q

What is the gravitational field strength of the earth

A

9.8 (N/Kg)

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18
Q

What is elastic potential energy

A

The energy stored in an elastic object when work is done on the object

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19
Q

How do you calculate elastic potential energy

A

1/2 x spring constant (K) x extension (E^2)

20
Q

What is thermal energy

A

The energy contained within a system that is responsible for its temperature

21
Q

How can thermal enegry be calculated

A

Mass(m) x specific heat capacity(c) x change in temperature

22
Q

What is specific heat capacity of a substance

A

The amount of energy required to raise the temperature of 1kg of a substance by 1*

23
Q

What does it mean if a substance has a low specific heat capacity

A

It takes less energy to change its temperature

24
Q

What does it mean if a substance has a high specific heat capacity

A

It takes more energy to change its temperature

25
Q

What the purpose of knowing the specific heat capacity of a substance

A

It determines how useful the substance would be for a specific purpose

26
Q

What are the variables in the specific heat capacity practical

A

Independant variable= time
Dependant variable= temperature
Control variable= material of block, current supplied

27
Q

What equipment is needed in the specific heat capacity practical

A

Block of metal, ammetre, voltmetre, thermometre, immersion heater, power supply, stopwatch

28
Q

What is step 1 of the specific heat capcity practical

A

Assemble the apparatus by placing the heater into the top of the block

29
Q

What is step 2 of the specific heat capacity practical

A

Measure the initial temperature of the block using the thermometre

30
Q

What is step 3 of the specific heat capcity practical

A

Turn on the power and start the stopwatch

31
Q

What is step 4 of the specific heat capacity practical

A

Take periodic measurements every 1 min of the voltage and the current from the voltmetre and ammetre

32
Q

What is step 5 of the specific heat capacity practical

A

Switch off power supply, stop stopwatch and let apporetus cool

33
Q

What is step 6 of the specific heat capacity practical

A

Monitor the themometer and record final temperature

34
Q

What is a systematic error that could happen in the specific heat capacity practical

A

Zero error

35
Q

Give one way to prevent random error in this practical

A

Make sure temperature value is read at eye leval to avoid parallat error

36
Q

What is mechanical work

A

A force that acts over a distance. For example a person pushing a box across a floor

37
Q

What is power

A

The rate of which work is done

38
Q

How do you calculate power

A

Energy(j)/time(t)

39
Q

What is the power,energy,time formula triangle and how do you use it

A

———-Energy(j)————Cover up the quantity you are calculating. If the other two are on the same
Power(p)——–Time(t) Multiply themand if one is above another you should devide top one by
bottom one

40
Q

What is the law of coservation of energy

A

Energy cant be created or destroyed it can only be transferred from one to another

41
Q

What is useful energy

A

Energy that is transferred from store to store and used for an intended purpose

42
Q

What is wasted energy

A

Energy that is not useful for the intended purpose and is dissipated to its surroundings

43
Q

What is thermal conduction

A

Thermal conduction is the diffusion of thermal energy (heat) within one or between multiple materials

44
Q

What does the thermal conductivity of a material determine

A

The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material

45
Q

Give 3 examples of substances with high thermal conductivity

A

Diamond
Aluminium
Graphite

Physics (5 decks)

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