Physics paper 1

• Energy is transferred between stores

  Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear
• Energy is transferred...


  Mechanically (by a force doing work), electrically (work done by moving charges), by heating or by radiation (like light or sound)
• When a system changes, energy is transferred


  It can be transferred into or away from the system, between objects in the system or between different types of energy stores. Closed systems are where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always 0
• kinetic energy


  energy of motion - the greater an object's mass and the faster it is going, the more energy there will be in its kinetic energy store. Ek (j) = 1/2m(kg)v(m/s) squared
• Raised objects store energy in gravitational potential energy stores


  lifting an object in a gravitational field requires work, causing an energy transfer to the the GPE store of the object. Ep(j) = m(kg)g(n/kg)h(m)
• Falling objects transfer energy

  Falling objects transfer energy from its GPE store to its kinetic energy store. When there's no air resistance, energy lost from the GPE store = energy gained in the kinetic energy store
• Stretching transfers energy to elastic potential energy stores

  As long as the limit of proportionality has not been exceeded, Ee (j) = 1/2 k (N/m) e (m) squared
• specific heat capacity


  the energy required to raise the temperature of one gram of a substance by one degree Celsius. 🔼E (j) = m(kg) c(j/kgdegree) 🔼theta (degrees Celsius)
• Conservation of energy principle

  Energy can be transferred but can never be created of destroyed
• Dissipated energy


  energy used up in a system, typically lost due to work done by friction, 'wasted energy
• Phone energy


  When you use the phone, energy is usefully transferred from the chemical energy store of the battery in the phone, but some of this energy is dissipated to thermal energy
• Closed system energy transfer

  A cold spoon is dropped into hot soup in an insulated flask, which is then sealed. Energy is transferred from the thermal energy store of the soup to the useless thermal energy of the spoon
• Power


  The rate at which work is done (watts). P(w) = E(j) / t(s)
• Powerful machine


  One which transfers a lot of energy in a short space of time
• Conduction occurs mainly in solids

  Conduction is the process where vibrating particles transfer energy to neighbouring particles.
• Long definition of conduction

  Energy transferred to an object by heating is transferred to the thermal store, which is shared across the kinetic store of the particles. The particles' collisions cause energy to be transferred between particles kinetic energy stores.
• thermal conductivity


  the Mrs sure of the rate at which thermal energy can travel through a material
• Convection occurs only in liquids and gases


  Convection is where energetic particles move away from hotter to cooler regions
• Convection longer definition


  Unlike in solids, the particles in liquids and gases are able to move. When you heat a region of a gas/liquid, the particles move faster and the space between particles increases. This causes the density of the region to decrease. Because they can flow, the warmer and less dense region will rise above denser cooler regions. If there is a constant heat source, a convection current will be made
• Radiators - convection currents


  Energy is transferred from the radiator to nearby air particles by conduction. The air by the radiator becomes warmer and less dense. This warm air rises and is replaced by cooler air. At the same time, the previously heated air transfers energy to the surrounding and cools, becomes denser, and sinks. This cycle repeats and causes a flow of air to circulate around the room
• How to reduce unwanted energy transfers

  Lubrication and thermal insulation
• Lubrication reduces frictional forces


  When something moves, there's at least one frictional force acting on it, causing some energy to be dissipated. For objects that are rubbed together, lubricants reduce the fiction between the object's surfaces when moved. Lubricants tend to be liquids (like oil) to flow easily between objects and coat them
• Insulation reduces the rate of energy transfer by heating


  Things to do to prevent energy loss through heating...

  - have think walls made from low thermal conductivity material. This makes the rate of energy transfer slower, so the building will cool more slowly.

  - use thermal insulation
• Thermal insulation examples


  - cavity walls made of an inner and outer wall with an air gap in between to reduce the amount of energy transferred by conduction.

  - loft insulation can reduce convection currents created in lofts

  - double glazed windows have an air gap between two layers of glass to prevent energy transfer by conduction

  - draught excluders around doors and windows reduce energy transfers by convection
• Most energy transfers involve some waste energy

  Efficiency = useful output energy transfer / total input energy transfer OR efficiency = useful power output / total power input
• Non renewable energy resources will one day run out


  Fossil fuels and nuclear fuels. Fossil fuels are typically burnt to provide coal, oil, and natural gas. They damage the environment but provide most of our energy
• Renewable energy resources will never run out

  These are: the sun, wind, water waves, hydro-electricity, bio-fuel, tides, geothermal. Most of them do damage to the environment, but in less nasty ways than non renewables. However, they don't provide much energy and some are unreliable as they depend on the weather
• Energy resources can be used for transport

  Non renewable - petrol and diesel powered vehicles use fuel from oil. Coal can be used in old fashioned steam trains to boil water for steam.

  Renewable - vehicles running on bio-fuels or a mix of a bio-fuel and petrol/diesel.

  Electricity sometimes powers vehicles and can be generated using renewable or non renewable resources
• Energy resources can also be used for heating

  Non renewable - natural gas is widely used for heating homes. The gas heats water, which gets pumped into radiators. Coal is commonly burnt in fireplaces. Electric heaters use electricity generated from non renewable resources.

  Renewable - a geothermal heat pump uses geothermal energy resources to heat buildings. Solar water heaters use to the sun to heat water, which gets pumped into radiators.
• Wind power


  This involves putting up lots of wind turbines in an exposed place, like on coasts. The turbines have a generator inside them - the rotating blades turn the generator to produce electricity.
• wind power advantages


  There's limited pollution (only when they're first manufactured), no fuel costs and minimal running costs, no permanent damage to the landscape
• wind power disadvantages


  They spoil the view, very noisy, unreliable as they depend on the weather, initial costs are quite high
• Solar cells


  They generate electric currents from the sun. They are often the best energy source to charge calculator or watch batteries, as they don't use much electricity.
• solar power advantages


  There's no pollution (although they use a lot of energy to manufacture), reliable in sunny countries in the daytime, energy is free and running cost extremely low
• solar power disadvantages


  Unreliable because they depend on weather, can't increase power output when there is extra demand, initial costs are high school
• Geothermal power


  This is energy in underground thermal energy stores. It is possible in volcanic areas or where hot rocks lie close to the surface. The source of a lot of this energy is the slow decay of various radioactive elements deep inside the earth
• Geothermal power advantages


  Free energy that is reliable and does very little damage to the environment. Can be used to generate electricity or heat buildings
• Geothermal power disadvantages


  There aren't many suitable locations for power plants, and the cost of building a power plant is high compared to the amount of energy that it produces
• hydroelectric power used falling water

  It tends to require the flooding of a valley by building a dam. Water is allowed out through turbines
• Hydro-electric power advantages


  There is no pollution and it can provide an immediate response to an increased demand for electricity. It is reliable and there are no fuel costs and minimal running costs