✅1. Energy Flashcards
(34 cards)
What is a system?
A system is an object or group of objects
e.g. an apple
What happens when a system changes?
When a system changes, the way energy is stored changes
For example, a kettle transfers electrical energy to chemical energy
What is Kinetic Energy?
& formula
- Kinetic energy is the the energy of a moving object
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Ek = 1/2 m v2
Kinetic Energy = 1/2 x mass x velocity2
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Ek in Joules
Mass in kg
Velocity in m/s
What is Elastic Potential Energy?
& formula
- Elastic Potential Energy is the energy stored when an object is stretched or squashed
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Ee = 1/2 k e2
Elastic Potential Energy = 1/2 x spring constant x extension2
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Ee in Joules
Spring Constant in N/m
Extension in m
What is Gravitational Potential Energy?
& formula
- Gravitational Potential Energy is the energy of an object when it is raised above ground level
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Ep = m g h
Gravitational Potential Energy = mass x gravitaional field strength x height
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Ep in Joules
Gravitaional Field Strength in N/m
Height in m
What is Specific Heat Capacity
The amount of energy needed to raise the temperature of 1kg of a substance by 1°C
What is the formula for calculating the amount of thermal energy stored in or released from a system as the temperature changes?
ΔE = m c Δθ
Change in thermal energy = mass x specific heat capacity x temperature change
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Change in thermal energy in Joules
Mass in kg
Specific Heat Capacity in J / Kg (per) °C
Temperature Change in °C
Define Power
Power is the rate at which energy is transferred or the rate at which work is done
Formula for Power
Power = Energy Transferred / Time
P = E / t
Power = Work Done / Time
P = W / t
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Power in Watts
Energy Transferred / Work Done in Joules
Time in Seconds
What is 1 watt equal to?
In terms of energy
1 watt = 1 joule per second
Give one example that illustrates the defenition of power
Two electric motors that both lift the same weight through the same height, but one does it faster than the other
What is the law of conserveration of energy?
Energy cannot be created or destroyed, it can only be transferred from one store to another
When happens to the total energy when there are energy transfers in a closed system?
There is no net change to the total energy
What is wasted energy?
Wasted energy is energy that is dissipated or stored in less useful ways
Give 3 common examples of wasted energy transfer?
- heat
- light
- sound
Explain ways of reducing unwanted energy transfers
We can reduce unwanted energy transfers by:
- Using lubrication for friction, so less thermal energy is lost as heat
- Using thermal insulation to prevent energy dissipating into the thermal energy store of the surroundings
What does it mean if a material has high thermal conductivity?
If a material has a high rate of thermal conductivity, it means it has a high rate of energy transfer by conduction across the material (it can transfer the energy easily)
Which factors affect the rate of cooling of a building?
- Thickness of the walls
- (Low/High) Thermal conductivity of the walls
State 3 methods of reducing heat loss in a building
- Double glazing windows
- Loft and wall insulation
- Thicker walls
- Aluminium foil behind radiators
What are the 2 formulas for efficiency?
How can we increase the efficiency of an intended energy transfer?
We can increase the efficiency of energy transfer by reducing the wasted energy output
How can the efficiency of boiling water in a pan be improved?
The efficiency of boiling water in a pan can be improved by placing a lid on the pan to reduce heat loss
How can the efficiency of a machine with moving parts be improved?
The efficiency of a machine with moving parts can be improved by lubricating any moving parts to reduce friction and therefore reduce energy loss due to heating
What are the main renewable and non-renewable energy resources?
Non-renewable:
- Fossil Fuels (coal, oil, gas)
- Nuclear Fuel
Renewable:
- Biofuel
- Wind
- Hydro-electricity
- Geothermal
- Tidal
- Solar
- Water waves
