Major Topics Low stakes topics TJNOTES
GCSE Physics Notes
PAPER I
Energy
Energy stores and systems
• When energy is transferred to an object, the energy is stored in one of the
object’s energy stores
The stores that you need to know are:
(1) Kinetic – energy stored in a moving object
(2) Thermal – all objects have thermal energy stores. The higher the
temperature, the more thermal energy it stores
(3) Chemical – energy stored in substances that can release the energy by a
chemical reaction. This includes food, fuels and even our muscles – often what
you’ll find is that you have to say that “chemical energy stored in muscles is
transferred to kinetic energy”
(4) Gravitational potential energy – stored in objects with mass and are inside
a gravitational field
(5) Elastic potential energy – stored in stretched or compressed objects
(6) Electrostatic energy – stored in objects with an electric charge interacting
with another electric charge
(7) Magnetic energy – stored in magnets that are interacting with other
magnetic material
(8) Nuclear – energy stored in atomic nuclei released in nuclear reactions
• A system is an object or a group of objects
• Closed systems are systems where neither matter nor energy can enter or leave
and so the net change in total energy is always zero
• When a system changes, energy is transferred – this can either be into or away
from a system, between different objects or between different types of energy
stores within a system
,Major Topics Low stakes topics TJNOTES
We can transfer energy between stores (do work) in 3 different ways:
(1) Mechanically – this involves doing work by exerting a force on an object and
moving it
(2) Electrically – a current moving through a potential difference can do work
(3) By heating – energy can be transferred from a hotter object to a colder
object and through radiation when energy is transferred by waves
You need to describe all the changes involved in the way energy is stored
when a system changes for common situations. For example:
(1) Projecting an object upwards
• The chemical energy store in the person’s muscle decreases and the energy is
transferred to the kinetic energy stores of the object. As its altitude increases, the
kinetic energy stores decrease as kinetic energy is transferred to gravitational
potential energy, so the gravitational potential energy stores increase. Some of
the kinetic energy is dissipated as thermal energy to the surroundings due to air
resistance acting on the object
(2) A moving object hitting an obstacle
• The kinetic energy decreases as it is transferred to the thermal energy stores of
the obstacle due to friction. The thermal energy stores of the obstacle increase,
leading to the energy being dissipated
(3) A vehicle slowing down is the same principle of kinetic energy being
transferred to thermal energy in the brake pads. The energy is dissipated as
kinetic energy stores of the car decrease and thermal energy stores in the breaks
increase due to work being done by friction
(4) Bringing water to boil in a kettle
• Energy is transferred from the electrostatic stores in the wires to thermal energy
in the heating element. This thermal energy is transferred to the thermal energy
stores in the water, causing it to boil
• Work done is just another way of saying energy transferred – they’re very
similar
• Work done also involves an energy transfer but takes place when a force moves
an object through a distance or by a moving charge doing work against
resistance in a circuit
,Major Topics Low stakes topics TJNOTES
• Energy always obeys the law of conservation of energy
• Energy can be transferred usefully, stored or dissipated but can never be created
or destroyed
• When energy is transferred between stores, not all of the energy is transferred
usefully to the store you want it to
• Some energy is always dissipated when an energy transfer takes place – the
energy is wasted/stored in a way that is not useful (dissipation is usually by
energy transfer to the thermal energy stores of the surroundings)
, Major Topics Low stakes topics TJNOTES
• The law of conservation of energy explains why the total energy in a closed
system is always the same: no energy can enter or leave the closed system, and,
since energy cannot be created or destroyed, the total energy is always the same
Changes in energy
• Any moving object has a store of kinetic energy, energy is transferred to this
store when it speeds up and energy transferred away when it slows down
• To calculate the kinetic energy of a moving object, we use the equation:
1
𝐸𝑘 = 𝑚𝑣 2
2
• Kinetic energy = 0.5 x mass x velocity2
• Energy is measured in Joules (J)
• Mass is measured in kg
• Velocity is measured in m/s
• When lifting an object in a gravitational field, work is done: energy is transferred
to the gravitational potential energy stores of the object
• To calculate energy transferred to gravitational potential energy, use the
equation:
𝐸𝑝 = 𝑚𝑔ℎ
• Gravitational potential energy = mass x gravitational field strength x height
• Energy is measured in Joules (J)
• Mass is measured in kg
• Gravitational field strength is measured in N/kg
• Height is measured in m
• Tip: when doing calculations, give final answer to lowest number of significant
figures
• Energy is transferred to elastic potential energy stores when an object is
compressed or stretched
• To calculate elastic potential energy, use the equation:
1
𝐸𝑒 = 𝑘𝑒 2
2
• Elastic potential energy = 0.5 x spring constant x extension 2
GCSE Physics Notes
PAPER I
Energy
Energy stores and systems
• When energy is transferred to an object, the energy is stored in one of the
object’s energy stores
The stores that you need to know are:
(1) Kinetic – energy stored in a moving object
(2) Thermal – all objects have thermal energy stores. The higher the
temperature, the more thermal energy it stores
(3) Chemical – energy stored in substances that can release the energy by a
chemical reaction. This includes food, fuels and even our muscles – often what
you’ll find is that you have to say that “chemical energy stored in muscles is
transferred to kinetic energy”
(4) Gravitational potential energy – stored in objects with mass and are inside
a gravitational field
(5) Elastic potential energy – stored in stretched or compressed objects
(6) Electrostatic energy – stored in objects with an electric charge interacting
with another electric charge
(7) Magnetic energy – stored in magnets that are interacting with other
magnetic material
(8) Nuclear – energy stored in atomic nuclei released in nuclear reactions
• A system is an object or a group of objects
• Closed systems are systems where neither matter nor energy can enter or leave
and so the net change in total energy is always zero
• When a system changes, energy is transferred – this can either be into or away
from a system, between different objects or between different types of energy
stores within a system
,Major Topics Low stakes topics TJNOTES
We can transfer energy between stores (do work) in 3 different ways:
(1) Mechanically – this involves doing work by exerting a force on an object and
moving it
(2) Electrically – a current moving through a potential difference can do work
(3) By heating – energy can be transferred from a hotter object to a colder
object and through radiation when energy is transferred by waves
You need to describe all the changes involved in the way energy is stored
when a system changes for common situations. For example:
(1) Projecting an object upwards
• The chemical energy store in the person’s muscle decreases and the energy is
transferred to the kinetic energy stores of the object. As its altitude increases, the
kinetic energy stores decrease as kinetic energy is transferred to gravitational
potential energy, so the gravitational potential energy stores increase. Some of
the kinetic energy is dissipated as thermal energy to the surroundings due to air
resistance acting on the object
(2) A moving object hitting an obstacle
• The kinetic energy decreases as it is transferred to the thermal energy stores of
the obstacle due to friction. The thermal energy stores of the obstacle increase,
leading to the energy being dissipated
(3) A vehicle slowing down is the same principle of kinetic energy being
transferred to thermal energy in the brake pads. The energy is dissipated as
kinetic energy stores of the car decrease and thermal energy stores in the breaks
increase due to work being done by friction
(4) Bringing water to boil in a kettle
• Energy is transferred from the electrostatic stores in the wires to thermal energy
in the heating element. This thermal energy is transferred to the thermal energy
stores in the water, causing it to boil
• Work done is just another way of saying energy transferred – they’re very
similar
• Work done also involves an energy transfer but takes place when a force moves
an object through a distance or by a moving charge doing work against
resistance in a circuit
,Major Topics Low stakes topics TJNOTES
• Energy always obeys the law of conservation of energy
• Energy can be transferred usefully, stored or dissipated but can never be created
or destroyed
• When energy is transferred between stores, not all of the energy is transferred
usefully to the store you want it to
• Some energy is always dissipated when an energy transfer takes place – the
energy is wasted/stored in a way that is not useful (dissipation is usually by
energy transfer to the thermal energy stores of the surroundings)
, Major Topics Low stakes topics TJNOTES
• The law of conservation of energy explains why the total energy in a closed
system is always the same: no energy can enter or leave the closed system, and,
since energy cannot be created or destroyed, the total energy is always the same
Changes in energy
• Any moving object has a store of kinetic energy, energy is transferred to this
store when it speeds up and energy transferred away when it slows down
• To calculate the kinetic energy of a moving object, we use the equation:
1
𝐸𝑘 = 𝑚𝑣 2
2
• Kinetic energy = 0.5 x mass x velocity2
• Energy is measured in Joules (J)
• Mass is measured in kg
• Velocity is measured in m/s
• When lifting an object in a gravitational field, work is done: energy is transferred
to the gravitational potential energy stores of the object
• To calculate energy transferred to gravitational potential energy, use the
equation:
𝐸𝑝 = 𝑚𝑔ℎ
• Gravitational potential energy = mass x gravitational field strength x height
• Energy is measured in Joules (J)
• Mass is measured in kg
• Gravitational field strength is measured in N/kg
• Height is measured in m
• Tip: when doing calculations, give final answer to lowest number of significant
figures
• Energy is transferred to elastic potential energy stores when an object is
compressed or stretched
• To calculate elastic potential energy, use the equation:
1
𝐸𝑒 = 𝑘𝑒 2
2
• Elastic potential energy = 0.5 x spring constant x extension 2
