- A system refers to an object or group of objects.
- Understanding the changes in energy storage involved in different situations is essential to understanding the behavior of systems.
- When an object is projected upwards, its potential energy increases and its kinetic energy decreases as it moves against the force of gravity.
- When a moving object hits an obstacle, its kinetic energy decreases, and its potential energy and elastic potential energy increase as it deforms the obstacle.
- When an object is accelerated by a constant force, its kinetic energy increases, and its potential energy and work done by the force increase as it moves in the direction of the force.
- When a vehicle slows down, its kinetic energy decreases, and its potential energy and work done by friction increase as it comes to a stop.
- When water is brought to a boil in an electric kettle, the electrical energy supplied is converted into thermal energy, increasing the internal energy of the water and the kettle.
- Kinetic energy is the energy possessed by a moving object and can be calculated using the equation: kinetic energy = 0.5 × mass × speed^2.
- The unit of kinetic energy is joules (J), which is the same as the unit of work or energy.
- The kinetic energy of an object increases with its speed and mass.
- The equation for calculating kinetic energy assumes that the object is moving in a straight line at a constant speed.
- Elastic potential energy is the energy stored in a stretched spring and can be calculated using the equation: elastic potential energy = 0.5 × spring constant × extension^2.
- The unit of elastic potential energy is also joules (J).
- The spring constant is a measure of the stiffness of the spring and is measured in newtons per metre (N/m).
- The extension is the change in length of the spring from its original length and is measured in metres (m).
- Gravitational potential energy is the energy an object gains when it is raised above the ground level and can be calculated using the equation: gravitational potential energy = mass × gravitational field strength × height.
- The unit of gravitational potential energy is also joules (J), and the value of the gravitational field strength (g) is given in the equation.
- The equation for calculating the amount of energy stored in or released from a system as its temperature changes is given as: change in thermal energy = mass × specific heat capacity × temperature change.
- The unit of thermal energy is joules (J), which is the same as the unit of work or energy.
- The mass in the equation refers to the mass of the system undergoing a change in temperature, and it is measured in kilograms (kg).
- The specific heat capacity is a property of a substance and is measured in joules per kilogram per degree Celsius (J/kg°C).
- 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.
- Power is a measure of the rate at which energy is transferred or the rate at which work is done.
- The equation for power is given as: power = energy transferred/time or power = work done/time.
- The unit of power is watts (W), which is the same as the unit of energy per unit time.
- The energy transferred in the equation refers to the amount of energy that is transferred from one object to another, and it is measured in joules (J).
- The time in the equation refers to the time taken for the energy transfer or work to be done, and it is measured in seconds (s).
- The work done in the equation refers to the amount of work that is done on an object, and it is also measured in joules (J).
- An energy transfer of 1 joule per second is equal to a power of 1 watt.
- Power is a scalar quantity, meaning that it has magnitude but no direction.
- The definition of power can be illustrated using examples, such as comparing two electric motors that both lift the same weight through the same height but one does it faster than the other.
- Energy is a fundamental property of matter and cannot be created or destroyed, only transferred or stored.
- Energy can be transferred usefully, meaning it can be used to do work or perform useful tasks, or it can be stored for later use.
- Energy can also be dissipated, meaning it is transferred into less useful forms or lost to the surroundings.
- In a closed system, the total energy remains constant, meaning that the energy transferred into the system is equal to the energy transferred out of the system.
- Examples of energy transfers in a closed system include the transfer of heat from one object to another or the transfer of electrical energy from a battery to a circuit.
- In all system changes, some energy is dissipated or wasted, often in the form of heat or sound energy.
- Ways of reducing unwanted energy transfers include the use of lubrication to reduce frictional energy losses and thermal insulation to reduce heat losses.
- The thermal conductivity of a material refers to its ability to conduct heat and can affect the rate of energy transfer by conduction across the material.
- The rate of cooling of a building is affected by the thickness and thermal conductivity of its walls, as well as other factors such as the type of insulation used.
- The energy efficiency of any energy transfer is a measure of how much useful output energy is obtained from the total input energy.
- The equation for calculating energy efficiency is given as: efficiency = useful output energy transfer/total input energy transfer.
- The efficiency of an energy transfer can also be calculated using the equation: efficiency = useful power output/total power input.
- The unit of energy efficiency is a dimensionless quantity, meaning it has no units.
- The main energy resources available for use on Earth include fossil fuels (coal, oil, and gas), nuclear fuel, bio-fuel, wind, hydroelectricity, geothermal energy, the tides, the Sun, and water waves.
- Renewable energy resources are those that can be replenished as they are used, while non-renewable resources are finite and cannot be replenished.
- Energy resources are used for various purposes, including transport, electricity generation, and heating.
- Reliability is an important factor in determining the suitability of an energy resource, as some sources are more reliable than others.
- The use of energy resources can have environmental impacts, including air pollution, water pollution, and greenhouse gas emissions.
- Renewable energy sources generally have lower environmental impacts than non-renewable sources.
Category: AQA GCSE Physics
AQA GCSE Physics Atomic Structure Notes for Separates and Combined
Please see below a sample version of these notes. They cover the following sub topics.
The structure of an atom
Mass number, atomic number and isotopes
The development of the model of the atom (common content with chemistry)
Radioactive decay and nuclear radiation
Half-lives and the random nature of radioactive decay
Different half-lives of radioactive isotopes
Uses of nuclear radiation
Nuclear Fission (Physics Only)
Nuclear Fusion (Physics Only)
AQA GCSE Physics and Combined Energy Questions and answers
We have changed the Energy topic of the specification into questions and answers.
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