Energy Flashcards
(24 cards)
What type of energy store does a battery have?
Chemical
What type of energy store does a spring have?
Elastic Potential
What type of energy store does a blowtorch has?
Thermal
Energy cannot be…
created or destroyed
A basketball player throws the ball into the hoop. Describe the change in energy store that has taken place as the ball
Kinetic to Gravitational
Storage heaters contain bricks which warm up and store heat energy.
The bricks in this heater have a mass of 40 kg and are heated from 18 oC to 40 oC. If the specific heat capacity of the brick
material is 850 J/kg oC, calculate the change in thermal energy during heating.
Change in thermal energy = Mass x Specific Heat Capacity x Temperature Change
ΔE = m x c x Δθ
Temperature change Δθ = 40 – 18 = 22 oC
change in thermal energy ΔE = 40 x 850 x 22
ΔE = 748 000 J or 748 kJ
In a “closed” system ….
energy can be transferred but there is no net energy loss.
The energy transfer diagram for a mobile phone shows that 100 J of electrical energy produces 45 J of light energy and 36 J of sound energy.
How much thermal energy will be dissipated by the phone?
45 J + 36 J = 81 J
100 J – 81 J = 19 J
19 J of thermal energy will be dissipated
Describe how the thermal energy produced by a bus driving along a road is dissipated.
The thermal energy increases the kinetic energy of the air particles therefore warming up the surroundings.
. State why the total energy supplied to an electric fan must always equal the total energy transferred by the electric fan.
Energy can not be created or destroyed so:
total energy in = total energy out
- The diagrams show two different types of loft insulation. Fiberglass insulation & Wool insulation
- The wool needs to be thicker to have the same insulating properties. Explain which material has the highest thermal conductivity?
Wool has the highest thermal conductivity as it lets thermal energy through at a faster rate so a thicker layer is needed for the same insulation as the fiberglass.
Explain how trapped air reduces the rate of heat loss, in terms of thermal conductivity.
The air trapped inside the fiberglass acts as an insulator because air has a very low thermal conductivity and thermal energy can not pass through it easily.
The motor for a lift in a tall building uses 12 000 W of power. The lift and its passengers has a mass of 500 kg. The lift motor takes 10 s to raise the lift and its passengers through a height of 20 m.
Work out the percentage efficiency of the lift motor.
- Efficiency = power out x 100 ÷ power in
- Power out = 5000 N x 20m
- Efficiency = 10 000 x 100 = 83 %
The low energy bulb below uses 18 000 J of energy in one hour. If the efficiency of the low energy bulb is 78 %. Work out the amount of light energy given off by the bulb in one hours
- Efficiency = energy out x 100 ÷ energy in
- Energy out = 78 x 18 000 J = 14 040 J
What is a fossil fuel?
A fuel formed in the geological past from the remains of living organisms.
List all the renewable energy sources
Bio-Fuels, hydro-electricity, wind turbines, coal, solar power
List all the non-renewable energy sources
Oil, nuclear, wind turbines, wave energy
What is a renewable energy source?
An energy source that can be replenished as it is used.
Why are fossil fuels considered to be a more reliable energy resource than renewable energy sources?
Produce a consistent energy supply with no gaps in energy delivery.
Despite a large investment by the UK government in wind power, the amount of fossil fuel used has not seen a decline. Give a possible explanation for this.
UK is using more energy and wind power can not meet this rise in demand.
The UK government is committed to investing in a “blend” of energy types to provide the UK’s energy needs for the next 100
years. Give an advantage of this rather than using just coal.
Evens out any variations in supply or cost of the energy source. Using only coal, if supplies stopped or the cost went up greatly, this would have a great impact on the consumer.
A graph shows the world use of renewable energies over the past sixty years. Why has the use of wood increased very little over this time?
Limited supplies of wood and it takes a long time to grow new supplies. Also, pressure and legislation to prevent many trees from being cut down.
A lot of money has been invested in wind turbines. Why does this energy source not produce as much as any other renewable resource?
Each wind turbine only produces a small amount of electricity and not enough have been installed to match production from other renewable resources.
Describe how human activities have contributed to the greenhouse effect?
Burning fossil fuels for heating, transport and industry has led to a build up of carbon dioxide in the atmosphere (along with other greenhouse gases).
