Flashcards
Power - Whole Topic Flashcards
Cards in this deck (59)
- 1What are the types of energy? (Most Kids Hate Learning GCSE Energy Names)Magnetic energy, kinetic energy, heat (thermal) energy, light energy, gravitational potential, chemical energy, sound energy, elastic potential, electrical energy, nuclear energy
- 2What is the law of conservation of energy?Energy cannot be created or destroyed, only transferred from one form to another.
- 3What is the useful and wasted energy output of: TVuseful = light energy / sound energy
wasted = heat energy - 4What is the useful and wasted energy output of: lightbulbuseful = light energy
wasted = thermal energy - 5What is the useful and wasted energy output of: hairdryeruseful = thermal energy / kinetic energy
wasted = sound energy - 6What is the useful and wasted energy output of: a fanuseful = kinetic energy
wasted = sound energy - 7What is the equation for work done?work done = force x distance
- 8what is the symbol equation for work done?W = F X s
- 9what are the units of the work done equation?work done = Joules, J
force = Newtons, N
distance = Meters, M - 10a 20N weight is raised through a height of 0.4m. What is the work done?W = F x s
W = 20N x 0.4m
W = 8J - 11what is the work done equation (p.d. and charge)work done = potential difference x charge
W = V x Q
J = V x C - 12What is kinetic energy?Kinetic energy is the energy form of movement.
- 13What is potential energy?Potential energy is the energy of position.
- 14What is the equation for potential energy?kinetic energy = 1/2 x mass x (velocity)2
- 15what is the symbol equation for potential energy?Ek = 1/2 x m x (V)2
- 16what is the unit equation for kinetic energy?Kinetic energy = Joules, J
Mass = Kilograms, Kg
Velocity = meters per second, m/s
J = 1/2 x KG x m/s(2) - 17What is the equation for potential energy?potential energy = mass x gravity x height
- 18What is the symbol equation for potential energy?Ep = m x g x h
- 19what is the unit equation for potential energy?Elastic potential = Joules, J
Mass = Kilograms, Kg
Gravity = Newtons per kilogram N/Kg
Height = meters, M - 20A car travels at a speed of 20m/s and has a mass of 1200Kg. What is the kinetic energy?Ek = 1/2 x m x V(2)
Ek = 1/2 x 1200 x 20(2)
Ek = 240,000J - 21What do kinetic and potential energy have in common?they both equal each other.
- 22What is Hooke's law?The extension of an elastic object, such as a spring, is directly proportional to the force applied, provided that the limit of proportionality is not exceded.
- 23What is the elastic potential equation?Elastic energy = spring constant x extension
- 24what is the elastic potential unit equation?Ee = K x e
- 25what is the elastic potential unit equation?Elastic potential = Joules, J
Spring constant = Newtons/m, N/m
Extension = meters, m - 26what is specific heat capacity?The energy needed to raise the temperature of 1Kg of a substance by 1 degrees c.
- 27What does the rate of temperature depend on?1) its mass
2) the energy supplied
3) the type of substance - 28what is the specific heat capacity formula?Energy transferred = mass x specific heat capacity x temperature change
- 29what is the specific heat capacity symbol equation?E = M x C x ϴ
- 30What do storage heaters do?storage heaters are cost effective because they have a block of concrete inside which absorbs the energy during off peak hours of the night and releases the energy at a slow rate throughout the day, reducing costs. Concrete has a high specific heat capacity.
- 31a 1Kg block of compound A is heated, it increases its temperature from 10 degrees c to 20 degrees c. How much energy has been added to the block? C for compound A = 100J/kg degrees cE = m x C x ϴ
E = 1kg x 1000J x 10
E = 10,000J - 32What does power measure?power measures the amount of energy transferred by something each second. It is measured in Watts (1 watt = 2 joule of energy per second)
- 33What is the formula for power?power = energy transferred / time
- 34what is the symbol equation for power?P = E / T
- 35what are the units for the equation of power?power = watts, W
energy transferred = joules, J
time = seconds, s - 36If Sophie used her hair dryer for 20s and it uses 2J of energy what is the power?P = E / T
P = 2J / 20s
P = 0.1 W - 37What does the rate at which an object transfers energy depend on?- surface area
- the material of what it is made from
- the type of surface which the object is in contact with - 38what is conduction?conduction is when energy is transferred through direct contact, for example a hot mug to a table. The better of a conducter, the quicker the surface heats up.
- 39what is convection?The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way, convection currents that transfer heat from place to place are set up.
- 40what is radiation?radiation is a type of electromagnetic radiation, which involves waves rather than particles. This means that, unlike conduction and convection, radiation can even pass through the vacuum of space. This is why we can still feel the heat of the Sun, although it is 150 million km away from the Earth.
- 41What happens when a metal is heated?The free electrons gain kinetic energy. This means they move faster and carry the heat energy to other areas of the metal.
- 42What is the best insulator?The best insulator is a vacuum because conduction cannot happen because there are no particles. Particles in a gas are too far apart for collisions to happen properly.
- 43What are examples of insulators?polystyrene
foam
cotton wool
fibre glass - 44How do flasks reduce heat loss?Shiny coating on the inside reflects heat back inside. Plastic on outside as it is a poor conductor. Vacuum layer to prevent conduction. Extra inside layer to prevent radiation. Lid on top prevents convection and radiation.
- 45Heat is lost through: windows What can be done to prevent this?Insulation type: double glazing
Reduces by: conduction/convection
How does it work?: vacuum between two panels of glass - 46Heat is lost through: walls What can be done to prevent this?Insulation type: solid brick walls/cavity insulator
Reduces by: conduction
How does it work?: gaps in wall allow heat to escape - 47Heat is lost through: floors What can be done to prevent this?Insulation type: carpet
Reduces by: conduction
How does it work?: more particles which makes it harder to escape - 48Heat is lost through: windows (think fabric) What can be done to prevent this?Insulation type: curtains
Reduces by: conduction / convection
How does it work?: thicker material which has more particles - 49Heat is lost through: roof What can be done to prevent this?Insulation type: fibreglass
Reduces by: conduction/convection/radiation
How does it work?: fibres which has trapped air which is a poor conductor - 50Heat is lost through: doors What can be done to prevent this?Insulation type: draught excluders
Reduces by: convection
How does it work?: covers gaps in doors - 51gas > liquid > solid what happens at each of the arrows?gas which condenses>
liquid which freezes
solid (least energy) - 52solid < liquid < gassolid which melts<
liquid which evaporates<
gas (most energy) - 53How does evaporation happen?particles in a liquid are different in energies. Some have enough energy to escape from the liquid and become a gas. Bonds are broken in this process. Remaining particles in the liquid have lower average kinetic energy than before and so cool down and evaporate.
- 54how does condensation happen?particles in a fas have different energies. Some may have enough energy to remain as separate particles, particularly if the gas is cool. They come close together and bonds forms between them. energy is released because of this.
- 55How can you increase evaporation by clothes on the line?Weather is warm/sunny which gives particles more energy, making them evaporate quicker. Spreading clothes out increases surface area which allows the heat energy to have more area to evaporate. The weather should be windy (less humid)
- 56What is the equation for efficiency? (energy)useful output energy transfer
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total output energy transfer - 57what is the equation for efficiency (power)useful power input
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useful power output - 58What are the three fossil fuels?coal
oil
gas - 59what are the dangers of using fossil fuels?they release carbon dioxide which is a greenhouse gas which thickens the atmosphere and causes global warming