Physics

Seite 1

· To understand that the particle model can be used to explain the different states of matter

· To understand and apply the principle that the density of a material is defined by the equation:

· To recall that when substances change state (melt, freeze, boil, evaporate, condense or sublimate), mass is conserved.

· To understand that changes of state are physical changes; the change does not produce a new substance. If the change is reversed the substance recovers its original properties.

· To recall that energy is stored inside a system by the particles (atoms and molecules) that make up the system. This is called internal energy.

· To apply the idea that internal energy is the total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system.

Heat and temperature

· To know that heating changes the energy stored within the system by increasing the energy of the particles that make up the system. Heating causes either the temperature of the system to increase, or a change of state to happen.

Specific heat capacity

· To know that if the temperature of the system increases: the increase in temperature depends on the mass of the substance heated, what the substance is and the energy input to the system.

· To know and use the equation

Latent heat

· To know that if a change of state happens:

· The energy needed for a substance to change state is called latent heat. When a change of state occurs, the energy supplied changes the energy stored (internal energy), but not the temperature.

· Specific latent heat of fusion – change of state from solid to liquid.

· Specific latent heat of vaporisation – change of state from liquid to vapour.

· To know and use the equation :

Gas pressure

· To know that the molecules of a gas are in constant random motion. The temperature of the gas is related to the average kinetic energy of the molecules. The higher the temperature, the greater the average kinetic energy and so the faster the average speed of the molecules.

· To know that when the molecules collide with the wall of their container they exert a force on the wall. The total force exerted by all of the molecules inside the container on a unit area of the walls is the gas pressure.

Kinetic energy

· Apply the principle that the amount of energy stored by an object can be calculated. The equation to be used is:

Gravitation potential energy

· Apply the principle that the amount of energy stored by an object can be calculated.

Elastic potential energy

· Apply the principle that the amount of energy stored by an object can be calculated.

Work Done

· To apply the principle that a force does work on an object when the force causes a displacement of the object:

Work as the transfer of energy: electrical force

· To apply the principle that the amount of energy transferred by electrical work can be calculated using the equation:

Power

· To know that power is defined as the rate at which energy is transferred or the rate at which work is done.

Energy conservation

· To know that energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

· Describe examples where there are energy transfers in a closed system, that there is no net change to the total energy.

· Apply the idea that whenever there are energy transfers in a system only part of the energy is usefully transferred. The rest of the energy is dissipated so that it is stored in less useful ways. This energy is often described as being wasted.

Temperature gradient as the transfer of energy: Insulation

· To know that unwanted energy transfers can be reduced in a number of ways, for example, through lubrication and the use of thermal insulation.

· Describe how the rate of cooling of a building is affected by the thickness and thermal conductivity of its walls.

· Apply the idea that the higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material.

· U-values measure how effective a material is an insulator.

Efficiency

· To know that the energy efficiency for any energy transfer can be calculated using the equation:

Energy Resources.

Describe the main energy resources available for use on Earth. These include:

· fossil fuels (coal, oil and gas)

· nuclear fuel

· bio-fuel

· wind

· hydro-electricity

· geothermal

· the tides

· the Sun

· water waves.

· Distinguish between energy resources that are renewable and energy resources that are non-renewable.

· Compare the ways that different energy resources are used. The uses to include transport, electricity generation and heating.

Electric circuits

· Know that Circuit diagrams use standard symbols:

· Know that for electrical charge to flow through a closed circuit the circuit must include a source of potential difference

· Recall that electric current is a flow of electrical charge. The size of the electric current is the rate of flow of electrical charge. Charge flow, current and time are linked by the equation:

· Apply the principle that the current at any point in a single closed loop of a circuit has the same value as the current at any other point in the same closed loop.

· The current through a component depends on both the resistance of the component and the potential difference across the component. The greater the resistance of the component the smaller the current for a given potential difference (p.d.) across the component.

· Apply the principle that current, potential difference or resistance can be calculated using the equation:

· Know that The resistance of components such as lamps, diodes, thermistors and LDRs is not constant; it changes with the current through the component.

· Know that the resistance of a filament lamp increases as the temperature of the filament increases.

· The current through a diode flows in one direction only. The diode has a very high resistance in the reverse direction.

· The resistance of a thermistor decreases as the temperature increases.

· The resistance of an LDR decreases as light intensity increases.

· Know that there are two ways of joining electrical components, in series and in parallel. Some circuits include both series and parallel parts.

Know that for components connected in series:

· there is the same current through each component

· the total potential difference of the power supply is shared between the components.

· the total resistance of two components is the sum of the resistance of each component.

· resistance, R, in ohms, Ω

For components connected in parallel:

· the potential difference across each component is the same

· the total current through the whole circuit is the sum of the currents through the separate components

· the total resistance of two resistors is less than the resistance of the smallest individual resistor.

AC/DC

· Know that cells and batteries supply current that always passes in the same direction. This is called direct current (d.c.).

· An alternating current (a.c.) is one that changes direction. Mains electricity is an a.c. supply. In the UK it has a frequency of 50 Hz and is about 230 V.

3 pin plug

· Know that most electrical appliances are connected to the mains using three-core cable.

· The insulation covering each wire is colour coded for easy identification:

· live wire – brown

· neutral wire – blue

· earth wire – green and yellow stripes.

· The live wire carries the alternating potential difference from the supply. The neutral wire completes the circuit. The earth wire is a safety wire to stop the appliance becoming live.

· The potential difference between the live wire and earth (0 V) is about 230 V.The neutral wire is at or close to earth potential (0 V). The earth wire is at 0 V, it only carries a current if there is a fault.

Electric power

· Know that the power of a device is related to the potential difference across it and the current through it by the equation:

· Everyday electrical appliances are designed to bring about energy transfers.

· Describe how different domestic appliances transfer energy from batteries or a.c. mains to the kinetic energy of electric motors or the energy of heating devices.

· The amount of energy an appliance transfers depends on how long the appliance is switched on for and the power of the appliance.

· Work is done when charge flows in a circuit.

· The amount of energy transferred by electrical work can be calculated using the equation:

The National Grid

· The National Grid is a system of cables and transformers linking power stations to consumers.

· Electrical power is transferred from power stations to consumers using the National Grid.

· Step-up transformers are used to increase the potential difference from the power station to the transmission cables then step-down transformers are used to decrease, to a much lower value, the potential difference for domestic use.

· This is done because, for a given power, increasing the potential difference reduces the current, and hence reduces the energy losses due to heating in the transmission cables.