| What is power? | The rate of energy transfer (how much energy was transferred in a certain amount of time) |
| What is the conversation of energy? | Energy cannot be created or destroyed, only transferred. |
| What are energy stores? | What type of energy is stored within an object when its transferred. |
| What are the different types of energy? | Thermal energy store, Kinetic energy store, Gravitational potential energy store, Elastic potential energy store, Chemical energy store, Magnetic energy store, Electrostatic energy store and Nuclear energy store. |
| What are the different ways energy can be transferred? | Energy may be transferred mechanically, electrically, by heating or by radiation. |
| How do you mechanically transfer energy? | By a force like push or pull. |
| How do you electrically transfer energy? | By moving charges. |
| How does radiation transfer energy? | By light rays or sound. |
| How does heat transfer energy? | By a temperature change. |
| What is a system? | A fancy way of saying a single object or a group of objects that you're talking about. When it changes, energy is transferred. |
| What is a closed system? | Systems where neither matter or energy can leave or enter. The net change in the total energy is always zero in a closed system. |
| What is work done? | A way of saying 'energy transferred'. |
| How does a falling object transfer energy? | When something is dropped from a height, its gravitational potential energy store is transferred to the kinetic energy store since its falling instead of rising. |
| What happens to energy that has been lost from one store, and gained in another? | Energy lost from store is the same as the Energy gained in other store |
| What is Kinetic energy? | Anything that moves has energy in its kinetic store. |
| What is the formula for kinetic energy? | Eₖ (J) = ½ × Mass (KG) × Velocity² (m/s²) |
| A car of mass 2500 kg is travelling at 20 m/s. Calculate the energy in its kinetic energy store. | ½ × 2500 (KG) × 20² (m/s²) = 500,000 J |
| What is the formula for velocity? | √² ˣ ᵏᵉ⁄ₘₐₛₛ |
| What is gravitational potential energy? | Anything that has a height above the ground has energy in its gravitational potential store. |
| What is the formula for gravitational potential energy? | Eₚ (J) = Mass (KG) × Gravitational field strength (N/KG) × Height (M) |
| A 2.0 kg object is dropped from a height of 10 m. Calculate the speed of the object after it has fallen 5.0 m, assuming there is no air resistance. Give your answer to 2 significant figures. | 2 (KG) × 9.8 (N/KG) × 5 (M) = 98 J
Velocity = √² ˣ ⁹⁸⁄₂
= 9.8 N/M
We know that kinetic energy was 98 J because the total amount of energy that was lost in was store, is the same amount of energy gained in the other.
Since the question didn't tell us what the Gravitational field strength was, we use 9.8 N/KG. |
| What is elastic potential energy? | Anything that has been stretched or squashed has energy in its elastic potential store. |
| What is the formula for elastic potential energy? | Eₑ = ½× K (Spring Constant - N/M) × Extension (M) |
| What is specific heat capacity? | How much energy is needed to heat 1 KG of a substance by 1 °C. |
| What is the formula for specific heat capacity ? | ∆E (Change in Thermal energy - J) = Mass (KG) × C (Specific Heat Capacity - J/KG°C) × ∆θ (Temp. Change - °C)
∆ which is also the delta symbol, means 'change in'. |
| How much energy is needed to heat 2.00 kg of water from 10° to 100°C? The specific heat capacity of water is 4200 J/kg°C | 2 (KG) × 4200 (J/KG°C) × 90 (Temp. Change - C°) = 756,000 J |
| How does the formula triangle for Specific heat capacity help? | You can rearrange equations. |
| Find the final temperature of 5 kg of water, at an initial temperature of 5 °C, after 50 kJ of energy has been transferred to it. | ∆θ = ∆E ÷ Mass × C
⁵⁰⁰⁰⁰⁄₅ ₓ ₄₂₀₀ = 2.38..
2.38 + 5 = 7.38 °C
The reason to why the answer is 7.38 °C instead of 2.38 °C is because if the initial (starting) temperature was 5 °C, then the ending temperature will be 5 °C + ∆θ. |
| What is the conservation of energy? | Energy can never be created or destroyed, only transferred. |
| What does dissipated mean? | Energy that is wasted because its been transferred not a store its not useful in, (usually thermal energy stores). |
| How do mobile phones dissipate energy? | Mobile phones are a system. When its used, energy is USEFULLY transferred from the chemical energy store of the battery. However, some of the energy is dissipated to thermal stores, hence your phone heating up after a while. |
| What does power mean? | The rate of energy transfer or the rate of work done. |
| What is the formula for power? | P (Watts) = ᵉ ⁽ᴱⁿᵉʳᵍʸ ᵗʳᵃⁿˢᶠᵉʳʳᵉᵈ ⁻ ᴶᵒᵘˡᵉˢ⁾ ᴼᴿ ᵂᵒʳᵏ ᴰᵒⁿᵉ ⁽ᴶ⁾ ⁄ₜ ₍ₜᵢₘₑₛ ₋ ₛ₎ |
| What are watts? | 1 joule pf energy transferred per second. |
| A motor transfers 4.8 kJ of energy in 2 minutes. Calculate its power input. (3 marks) | P = ⁴⁸⁰⁰⁄₁₂₀ = 40 J
4.8 kJ = 4800 J - Energy transferred is in joules
2 minutes = 120 seconds - Time is in seconds |
| What does conduction mean and how does it happen? | When vibrating particles transfer energy to other particles, this happens mostly in solids.
Energy is transferred to an object by heating which is the thermal store of an object.
This energy is then shared to the kinetic energy stores of the particles which causes them to vibrate and collide, also transferring energy. This is conduction.
This continues throughout the object until it reaches the other side. The remaining energy is then transferred to its surroundings. |
| What is thermal conductivity? | The measure of how quickly energy is transferred through a material. |
| What does convection mean? | Convection is the transfer of heat by fluid particles moving from a hot to a cooler area. |
| What is lubrication? | A way to reduce unwanted energy transfers.
Whenever there's a frictional force, energy is dissipated. Lubricants reduce frictions between objects' surfaces when they move. |
| Whats an example of an object dissipating energy due to friction? | When a falling ball faces air resistance, transferring the falling objects kinetic energy store to the thermal energy store. |
| What is insulation? | When you use materials with low thermal conductivity to prevent heat loss. |
| What are cavity wall insulations? | The air gap between inner and outer walls are filled with foam to reduce convection and conduction. |
| What are loft insulations? | Fibreglass wool is used to reduce energy loss by conduction and to prevent convection currents. |
| What are double glazed windows? | A gap of air between two sheets of glass to prevent conduction. |
| What are draught excluders? | An object that is put against doors or windows to reduce energy transfers through convection. This may keeping heat from escaping or even from cold air from entering. |
| What does efficiency mean? | A comparison of the useful amount of energy transferred to the total amount of energy transferred. |
| What is the formula for efficiency? | Efficiency = ᵘˢᵉᶠᵘˡ ᵒᵘᵗᵖᵘᵗ ᵉⁿᵉʳᵍʸ ᵗʳᵃⁿˢᶠᵉʳ⁄ₜₒₜₐₗ ᵢₙₚᵤₜ ₑₙₑᵣ₉ᵧ ₜᵣₐₙₛₑᵣ |
| A motor in a remote controlled car transfers 300 J of energy into the cars energy store. 225 J are transferred into the cars kinetic energy stores. Calculate the efficiency of the motor. | Efficiency = ²²⁵⁄₇₅ = 3 |
| A machine has a useful power output of 900 W and a total power input of 1200 W. In a given time, 72 kJ of energy is transferred to the machine. Calculate the amount of energy usefully transferred by the machine in this time. | Efficiency = useful output / total input
⁹⁰⁰⁄₁₂₀₀ = 0.75
Useful output = total input × efficiency
0.75 × 72,000 = 54,000 J
72 kJ = 72,000 J |
| What is a non renewable energy resource? | Non renewable energy resources are fossil fuels and nuclear fuels that will eventually run out. They are reliable. |
| What is a renewable energy resource? | Energy resources that will never run out, but they don't provide a lot of energy so they are seen as unreliable. |
| What are some examples of non renewable energy resources? | Coal, Oil and natural gas |
| What are some examples of renewable energy resources? | Solar power, Wind, Water waves, Hydro-electricity, Bio-fuels, Tides and Geothermal |
| What can energy resources can be used for? | Transport - Petrol and diesel powered vehicles use non-renewable sources like oil, and coal is used in some steam trains to boil water to produce steam.
Vehicles that run on fire bio-fuels use renewable sources.
Heating - Natural gas, coal and electrical heaters are non-renewable sources that heat home in the UK.
Geothermal heat pump, solar water heaters and bio-fuels/ electricity are renewable sources to heat homes. |
| How do wind energy energy sources work? | Wind turbines, or windmills have a generator inside it, which rotate and produce electricity.
They don't pollute, but they spoil the view and you need about 1,500 to replace 1 coal-fired power station. They're noisy and if the wind stops or is too strong, the turbine won't spin. This means when there's a high demand its impossible to increase the supply.
The initial cost is high and they produce 75-80% of electricity. Its renewable. |
| How do solar power energy sources work? | Solar power generate electrical currents from sunlight. They have no pollution, and is very reliable in sunny areas.
Initial costs are high but the running costs are almost a nil. They are often best as energy sources to charge batteries in calculator and watches since they generate electricity to a small scale. Its renewable. |
| How do geothermal energy sources work? | Geothermal power - cold water is pumped down to hot rocks, and the steam created is used to power a turbine, to power a generator.
This is only possible near volcanic areas where hot rocks are near the surface.
It's reliable and it generates electricity or heat to buildings.
The main drawback is that there isn't many suitable locations and the cost of building the power plant can be high. It's a renewable source. |
| How do hydro-electricity energy sources work? | Hydro electricity - power from flooded valleys is used to start a generator.
A big dam is built and rainwater is caught and allowed through turbines, there's no pollution.
It destroys the environment and habitats, rotting vegetation releases methane and carbon dioxide and the reservoirs can look unsightly when they dry.
But, it can provide an immediate response, and there's no problem with availability unless there's a drought.
The costs are high but there's no fuels so there are low running costs.
Its good for generating in remote areas at a small scale. It is renewable. |
| How dowWave power energy sources work? | Wave power - There is no pollution but it disturbs the seabed and marine animals. They're fairly unremarkable;aoan;e since waves die down when the wind drops.
The initial cost is high but there is no fuel costs and minimal running costs.
Its useful on small islands. Its renewable. |
| How do tidal barrages energy sources work? | Tidal barrages - big damns are built across river estuaries with turbines in them. As the tide comes in, it fills the estuary, and the water is allowed out through the turbines at a controlled speed.
The tides are produced by the gravitational pull of the sun and moon.
It produces no pollution, but it prevents free access to boats and spoils the view. It also alters habitats.
Its reliable but the height go the tide may be a drawback.
The initial costs are moderately high, but it has minimal running costs. It creates a significant amount of energy and is renewable. |
| How do bio-fuels work? | Renewable energy resources created from plant products or animal dung.They can be solid, liquid or gas and burnt to produce electricity. |
| What are some pros of bio fuels? | Bio fuels are carbon neutral.
They are fairly reliable, due to the fact that crops take a short time to grow.
But they cannot respond to immediate energy demands. |
| What are some cons of bio fuels? | The cost for biofuels are high.
People believe that crops should be grown for food and that there isnt enough space or water to meet the demands.
Species have been losing their habitats due to the removing of forests.
The decay and burning of vegetation increases carbon dioxide and methane. |
| A laptop charger passes a current of 8 A through a laptop battery. Calculate, in minutes, how long the charger needs to be connected to the battery for 28,000 C of charge to be transferred. | T = Q ÷ I
28,800 ÷ 8
> 3600 seconds
= 60 minutes |
| What are the different energy stores? | Kinetic energy store, Thermal energy store, Elastic potential energy store, gravitational potential energy store and chemical energy store. |
| What is the formula for power? | Power = ᵉⁿᵉʳᵍʸ/ₜᵢₘₑ |
