AQA Physics P1 Flashcards
Why do you place a lid on a thermal flask?
To reduce heat loss by convection as it stops hot particles escaping.
What is the purpose of a vacuum in a vacuum flask?
Reduce heat loss due to conduction and convection as both of these need particles, and the vacuum has no particles.
Why do I make part of a vacuum flask out of plastic?
To reduce heat loss due to conduction as plastic is a bad conductor.
Why do animals in cold climates have small ears?
To reduce heat loss due to radiation by reducing the surface area.
How best do you design a radiator, or something you want to keep cool?
Paint it black and increase the surface area
Why does painting something black increase heat loss?
Black is the best absorber and emitter of radiation.
How can I increase the surface area of a radiator?
Add fins
What is a U-Value?
A measure of how good or bad a material is at keeping in heat.
What does a big U-value mean?
It is a poor insulator.
What is specific heat capacity?
The energy needed to raise 1 kg of material by 1 degree.
The bigger the temperature difference…
The faster the object transfers heat to its surroundings.
How do I increase the rate of heat transfer from an object?
Increase the surface area, make the object out of a conductor.
How do I figure out if its worth it to use an LED light bulb?
Figure out how many normal light bulbs you would use in its life time and calculate how much they’d have cost by considering both the cost of the bulb and the cost of using the bulb.
What goes in the left hand side of a Sankey diagram?
The input energy.
What goes out the bottom of a Sankey diagram?
The waste energy.
What goes out the right hand side of a Sankey diagram?
The useful energy.
What does the width of the arrows mean in a Sankey diagram?
What proportion of the energy is transferred by that arrow.
What is pretty much always the waste energy?
Heat
What does waste energy do to the surroundings?
Usually heats it up.
What is the energy transfer in a light bulb?
Electric to Light, with waste heat
How do I calculate the amount of energy used by an appliance in kilowatt-hours?
Take the time in HOURS, take the power in KILOWATTS, multiply them together.
How does a fossil fuel power plant work?
Burn fossil fuels, use them to heat and boil water, use the steam to push a turbine around, use the turbine to rotate a generator, the generator produces power.
How does pumped storage hydroelectric power work?
Let water fall from a height to push a turbine around, use the turbine to rotate a generator, the generator produces power.
How does a nuclear power plant work?
Produce nuclear fission, the “waste” heat and boil water, use the steam to push a turbine around, use the turbine to rotate a generator, the generator produces power.
What are the advantages of renewables? (e.g. wind, tidal, geothermal)
They are renewable, they do not produce greenhouse gases.
What are the disadvantages of renewables? (e.g. wind, tidal, geothermal)
They are unreliable, and they need to be placed in a specific location (for example, wind turbines need to be placed somewhere windy)
What is geothermal energy?
Heat from hot rocks in the ground is used to boil water, turn a turbine, turn a generator and produce electricity.
What are the disadvantages of fossil fuels?
The produce greenhouse gases and contribute to global warming, they are not renewable.
What are the advantages of fossil fuels?
They have high energy density, they are reliable.
Why do we use step-up transformers in the National Grid?
Increase the voltage, to decrease the current, to reduce the heat loss, to increase the efficiency.
Why do we use step-down transformers in the National Grid?
To decrease the voltage, so its safe for consumers.
What does “decommisioning” a nuclear power plant mean?
Removing the radioactive waste materials safely.
What do waves do?
Transfer energy using vibrations.