Physics paper 1

• Kinetic energy is directly proportional to the square of the velocity.
• Energy changes in a system involve the ways energy is stored before and after such changes, with examples like an object projected upwards, a moving object hitting an obstacle, and bringing water to a boil in an electric kettle
• Students should be able to calculate changes in energy involved when a system is changed by heating, work done by forces, work done when a current flows, and show on a common scale how the overall energy in a system is redistributed
• Kinetic energy of a moving object can be calculated using the equation: kinetic energy, Ek, in joules, J = 1/2 x mass, m, in kilograms x speed, v, in metres per second squared
• The amount of elastic potential energy stored in a stretched spring can be calculated using the equation: elastic potential energy, Ee, in joules = 1/2 x spring constant, k, in newtons per meter x extension, e, in meters squared
• The amount of gravitational potential energy gained by an object raised above ground level can be calculated using the equation: gravitational potential energy, Ep, in joules = mass, m, in kilograms x gravitational field strength, g, in newtons per kilogram x height, h, in meters
• The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation: energy change, ΔE, in joules = mass, m, in kilograms x specific heat capacity, c, in joules per kilogram per degree Celsius x temperature change, Δθ, in degrees Celsius
• Power is defined as the rate at which energy is transferred or the rate at which work is done
• Energy can be transferred usefully, stored, or dissipated, but cannot be created or destroyed
• The energy efficiency for any energy transfer can be calculated using the equation: efficiency = useful energy output / total energy input
• Main energy resources available for use on Earth include fossil fuels, nuclear fuel, biofuel, wind, hydroelectricity, geothermal, the tides, the Sun, and water waves
• Students should be able to describe the main energy sources available, distinguish between renewable and non-renewable energy resources, compare ways different energy resources are used, understand why some are more reliable, describe environmental impacts, and explain patterns and trends in energy resource use
• Electric charge is a fundamental property of matter, and understanding the microstructure of conductors, semiconductors, and insulators helps in designing components and building electric circuits
• Circuit diagrams use standard symbols, and students should be able to draw and interpret them
• Electric current is a flow of electrical charge, and the size of the electric current is the rate of flow of electrical charge
• The current through a component depends on both the resistance of the component and the potential difference across the component
• 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, and the total resistance of two components is the sum of the resistance of each component
• 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, and the total resistance of two resistors is less than the resistance of the smallest individual resistor
• Mains electricity in the UK has a frequency of 50 Hz and a potential difference of about 230 V
• In the UK, most electrical appliances are connected to the mains using three-core cable with color-coded insulation: brown for live wire, blue for neutral wire, and green and yellow stripes for the earth wire
• The live wire carries the alternating potential difference from the supply, the neutral wire completes the circuit, and the earth wire is a safety wire to prevent the appliance from becoming live
• The potential difference between the live wire and earth is about 230 V, while the neutral wire is at or close to earth potential (0 V), and the earth wire is at 0 V and only carries a current if there is a fault
• Students should be able to explain that a live wire may be dangerous even when a switch in the mains circuit is open, and the dangers of providing any connection between the live wire and earth
• The National Grid is a system of cables and transformers linking power stations to consumers, with step-up transformers increasing the potential difference for transmission and step-down transformers decreasing it for domestic use
• The National Grid system is an efficient way to transfer energy due to the use of transformers
• A charged object creates an electric field around itself, with the field being strongest close to the charged object and weaker further away; a second charged object in the field experiences a force that gets stronger as the distance decreases
• Students should be able to draw the electric field pattern for an isolated charged sphere and explain how the concept of an electric field helps to explain the non-contact force between charged objects and other electrostatic phenomena
• The particle model is used to predict the behavior of solids, liquids, and gases, with applications in everyday life such as designing vessels to withstand high pressures and temperatures
• The density of a material is defined by an equation, and students should be able to recall and apply this equation to changes where mass is conserved
• When substances change state, mass is conserved, and changes of state are physical changes that differ from chemical changes because the material recovers its original properties if the change is reversed
• Internal energy is the total kinetic and potential energy of all particles in a system, and heating changes the energy stored within the system by increasing the energy of the particles, raising the temperature or producing a change of state
• The specific heat capacity of a substance is the amount of energy required to raise the temperature of one kilogram of the substance by one degree Celsius
• The energy needed for a substance to change state is called latent heat, with specific latent heat of fusion for solid to liquid and specific latent heat of vaporization for liquid to vapor
• Students should be able to apply equations to calculate the energy change involved in changes of state and distinguish between specific heat capacity and specific latent heat
• The molecules of a gas are in constant random motion, and changing the temperature of a gas at constant volume changes the pressure exerted by the gas
• A gas can be compressed or expanded by pressure changes, with the pressure producing a net force at right angles to the wall of the gas container
• Increasing the volume in which a gas is contained, at constant temperature, can lead to a decrease in pressure
• Doing work on a gas increases its internal energy and can cause an increase in temperature, as seen in situations like a bicycle pump
• Ionising radiation, discovered over a century ago, took several decades for nuclear physicists to understand the structure of atoms, nuclear forces, and stability
• Early researchers suffered from exposure to ionising radiation, leading to the introduction of rules for radiological protection in the 1930s