GCSE Physics₈₄₆₃

GCSE Physics Specification Specification for first teaching in 2016

21 Sep 2015

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4.1 Energy

The concept of energy emerged in the 19^th century. The idea was used to explain the work output of steam engines and then generalised to understand other heat engines. It also became a key tool for understanding chemical reactions and biological systems.

Limits to the use of fossil fuels and global warming are critical problems for this century. Physicists and engineers are working hard to identify ways to reduce our energy usage.

4.1.1 Energy changes in a system, and the ways energy is stored before and after such changes

4.1.1.1 Energy stores and systems

Content	Key opportunities for skills development
A system is an object or group of objects. There are changes in the way energy is stored when a system changes. Students should be able to describe all the changes involved in the way energy is stored when a system changes, for common situations. F or example: an object projected upwards a moving object hitting an obstacle an object accelerated by a constant force a vehicle slowing down bringing water to a boil in an electric kettle. Throughout this section on Energy students should be able to calculate the changes in energy involved when a system is changed by: heating work done by forces work done when a current flows	The link between work done (energy transfer) and current flow in a circuit is covered in Energy transfers . WS 4.5
use calculations to show on a common scale how the overall energy in a system is redistributed when the system is changed.	WS 1.2 , 4.3, 4.5, 4.6 MS 1a, c, 3b, c

Content

Key opportunities for skills development

A system is an object or group of objects.

There are changes in the way energy is stored when a system changes.

Students should be able to describe all the changes involved in the way energy is stored when a system changes, for common situations. F or example:

an object projected upwards
a moving object hitting an obstacle
an object accelerated by a constant force
a vehicle slowing down
bringing water to a boil in an electric kettle.

Throughout this section on Energy students should be able to calculate the changes in energy involved when a system is changed by:

heating
work done by forces
work done when a current flows

The link between work done (energy transfer) and current flow in a circuit is covered in Energy transfers .

WS 4.5

use calculations to show on a common scale how the overall energy in a system is redistributed when the system is changed.

WS 1.2 , 4.3, 4.5, 4.6

MS 1a, c, 3b, c

4.1.1.2 Changes in energy

Content	Key opportunities for skills development
Students should be able to calculate the amount of energy associated with a moving object, a stretched spring and an object raised above ground level.	WS 1.2, 4.3, 4.4, 4.6 MS 1a, c, 3b, c
The kinetic energy of a moving object can be calculated using the equation: $k i n e t i c e n e r g y = 0.5 \times m a s s \times (s p e e d)^{2}$ $[E_{k} = \frac{1}{2} m v^{2}]$ kinetic energy, E _k , in joules, J mass, m , in kilograms, kg speed, v , in metres per second, m/s The amount of elastic potential energy stored in a stretched spring can be calculated using the equation:	MS 3b, c Students should be able to recall and apply this equation.
$e l a s t i c p o t e n t i a l e n e r g y = 0.5 \times s p r i n g c o n s t a n t \times (e x t e n s i o n)^{2}$ ${[E}_{e} = \frac{1}{2} k e^{2}]$ (assuming the limit of proportionality has not been exceeded) elastic potential energy, E _e , in joules, J spring constant, k , in newtons per metre, N/m extension, e , in metres, m The amount of gravitational potential energy gained by an object raised above ground level can be calculated using the equation:	MS 3b, c Students should be able to apply this equation which is given on the Physics equation sheet .
$g . p . e . = m a s s \times g r a v i t a t i o n a l f i e l d s t r e n g t h \times h e i g h t$ $[E_{p} = m g h]$ gravitational potential energy, E _p , in joules, J mass, m , in kilograms, kg gravitational field strength, g , in newtons per kilogram, N/kg (In any calculation the value of the gravitational field strength ( g ) will be given). height, h , in metres, m	MS 3b, c Students should be able to recall and apply this equation. AT 1 Investigate the transfer of energy from a gravitational potential energy store to a kinetic energy store.

Content

Key opportunities for skills development

Students should be able to calculate the amount of energy associated with a moving object, a stretched spring and an object raised above ground level.

WS 1.2, 4.3, 4.4, 4.6

MS 1a, c, 3b, c

The kinetic energy of a moving object can be calculated using the equation:

$k i n e t i c e n e r g y = 0.5 \times m a s s \times (s p e e d)^{2}$

$[E_{k} = \frac{1}{2} m v^{2}]$

kinetic energy, E _k , in joules, J

mass, m , in kilograms, kg

speed, v , in metres per second, m/s

The amount of elastic potential energy stored in a stretched spring can be calculated using the equation:

MS 3b, c

Students should be able to recall and apply this equation.

$e l a s t i c p o t e n t i a l e n e r g y = 0.5 \times s p r i n g c o n s t a n t \times (e x t e n s i o n)^{2}$

${[E}_{e} = \frac{1}{2} k e^{2}]$

(assuming the limit of proportionality has not been exceeded)

elastic potential energy, E _e , in joules, J

spring constant, k , in newtons per metre, N/m

extension, e , in metres, m

The amount of gravitational potential energy gained by an object raised above ground level can be calculated using the equation:

MS 3b, c

Students should be able to apply this equation which is given on the Physics equation sheet .

$g . p . e . = m a s s \times g r a v i t a t i o n a l f i e l d s t r e n g t h \times h e i g h t$

$[E_{p} = m g h]$

gravitational potential energy, E _p , in joules, J

mass, m , in kilograms, kg

gravitational field strength, g , in newtons per kilogram, N/kg (In any calculation the value of the gravitational field strength ( g ) will be given).

height, h , in metres, m

MS 3b, c

Students should be able to recall and apply this equation.

AT 1

Investigate the transfer of energy from a gravitational potential energy store to a kinetic energy store.

4.1.1.3 Energy changes in systems

Content	Key opportunities for skills development
The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation:
$c h a n g e i n t h e r m a l e n e r g y = m a s s \times s p e c i f i c h e a t c a p a c i t y \times t e m p e r a t u r e c h a n g e$ $[∆ E = m c ∆ θ]$ change in thermal energy, ∆ E , in joules, J mass, m , in kilograms, kg specific heat capacity, c , in joules per kilogram per degree Celsius, J/kg °C temperature change, ∆ θ , in degrees Celsius, °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.	MS 3b, c Students should be able to apply this equation which is given on the Physics equation sheet. This equation and specific heat capacity are also included in Temperature changes in a system and specific heat capacity .

Content

Key opportunities for skills development

The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation:

$c h a n g e i n t h e r m a l e n e r g y = m a s s \times s p e c i f i c h e a t c a p a c i t y \times t e m p e r a t u r e c h a n g e$

$[∆ E = m c ∆ θ]$

change in thermal energy, ∆ E , in joules, J

mass, m , in kilograms, kg

specific heat capacity, c , in joules per kilogram per degree Celsius, J/kg °C

temperature change, ∆ θ , in degrees Celsius, °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.

MS 3b, c

Students should be able to apply this equation which is given on the Physics equation sheet.

This equation and specific heat capacity are also included in Temperature changes in a system and specific heat capacity .

Required practical activity 1 : investigat ion to determine the specific heat capacity of one or more materials. The investigation will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase in thermal energy stored.

AT skills covered by this practical activity: AT 1 and 5.

This practical activity also provides opportunities to develop WS and MS. Details of all skills are given in Key opportunities for skills development .

4.1.1.4 Power

Content	Key opportunities for skills development
Power is defined as the rate at which energy is transferred or the rate at which work is done. $p o w e r = \frac{e n e r g y t r a n s f e r r e d}{t i m e}$ $[P = \frac{E}{t}]$ $p o w e r = \frac{w o r k d o n e}{t i m e}$ $[P = \frac{W}{t}]$ power, P , in watts, W energy transferred, E , in joules, J time, t , in seconds, s work done, W , in joules, J An energy transfer of 1 joule per second is equal to a power of 1 watt. Students should be able to give examples that illustrate the definition of power eg comparing two electric motors that both lift the same weight through the same height but one does it faster than the other.	MS 3b, c Students should be able to recall and apply both equations.

Content

Key opportunities for skills development

Power is defined as the rate at which energy is transferred or the rate at which work is done.

$p o w e r = \frac{e n e r g y t r a n s f e r r e d}{t i m e}$

$[P = \frac{E}{t}]$

$p o w e r = \frac{w o r k d o n e}{t i m e}$

$[P = \frac{W}{t}]$

power, P , in watts, W

energy transferred, E , in joules, J

time, t , in seconds, s

work done, W , in joules, J

An energy transfer of 1 joule per second is equal to a power of 1 watt.

Students should be able to give examples that illustrate the definition of power eg comparing two electric motors that both lift the same weight through the same height but one does it faster than the other.

MS 3b, c

Students should be able to recall and apply both equations.

4.1.2 Conservation and dissipation of energy

4.1.2.1 Energy transfers in a system

Content	Key opportunities for skills development
Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed. Students should be able to describe with examples where there are energy transfers in a closed system, that there is no net change to the total energy. Students should be able to describe, with examples, how in all system changes energy is dissipated, so that it is stored in less useful ways. This energy is often described as being ‘wasted’.
Students should be able to explain ways of reducing unwanted energy transfers, for example through lubrication and the use of thermal insulation. The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material. Students should be able to describe how the rate of cooling of a building is affected by the thickness and thermal conductivity of its walls. Students do not need to know the definition of thermal conductivity.	WS 1.4 AT 1, 5 Investigate thermal conductivity using rods of different materials.

Content

Key opportunities for skills development

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

Students should be able to describe with examples where there are energy transfers in a closed system, that there is no net change to the total energy.

Students should be able to describe, with examples, how in all system changes energy is dissipated, so that it is stored in less useful ways. This energy is often described as being ‘wasted’.

Students should be able to explain ways of reducing unwanted energy transfers, for example through lubrication and the use of thermal insulation.

The higher the thermal conductivity of a material the higher the rate of energy transfer by conduction across the material.

Students should be able to describe how the rate of cooling of a building is affected by the thickness and thermal conductivity of its walls.

Students do not need to know the definition of thermal conductivity.

WS 1.4

AT 1, 5

Investigate thermal conductivity using rods of different materials.

Required practical activity 2 (physics only): investigate the effectiveness of different materials as thermal insulators and the factors that may affect the thermal insulation properties of a material.

AT skills covered by this practical activity: AT 1 and 5.

This practical activity also provides opportunities to develop WS and MS. Details of all skills are given in Key opportunities for skills development .

4.1.2.2 Efficiency

Content	Key opportunities for skills development
The energy efficiency for any energy transfer can be calculated using the equation: $e f f i c i e n c y = \frac{u s e f u l o u t p u t e n e r g y t r a n s f e r}{t o t a l i n p u t e n e r g y t r a n s f e r}$ Efficiency may also be calculated using the equation: $e f f i c i e n c y = \frac{u s e f u l p o w e r o u t p u t}{t o t a l p o w e r i n p u t}$	MS 3b, c Students should be able to recall and apply both equations. MS 1a, c, 3b, c Students may be required to calculate or use efficiency values as a decimal or as a percentage.
(HT only) Students should be able to describe ways to increase the efficiency of an intended energy transfer.	(HT only) WS 1.4

Content

Key opportunities for skills development

The energy efficiency for any energy transfer can be calculated using the equation:

$e f f i c i e n c y = \frac{u s e f u l o u t p u t e n e r g y t r a n s f e r}{t o t a l i n p u t e n e r g y t r a n s f e r}$

Efficiency may also be calculated using the equation:

$e f f i c i e n c y = \frac{u s e f u l p o w e r o u t p u t}{t o t a l p o w e r i n p u t}$

MS 3b, c

Students should be able to recall and apply both equations.

MS 1a, c, 3b, c

Students may be required to calculate or use efficiency values as a decimal or as a percentage.

(HT only) Students should be able to describe ways to increase the efficiency of an intended energy transfer.

(HT only) WS 1.4

4.1.3 National and global energy resources

Content	Key opportunities for skills development
The main energy resources available for use on Earth include: fossil fuels (coal, oil and gas), nuclear fuel, bio-fuel, wind, hydro-electricity, geothermal, the tides, the Sun and water waves. A renewable energy resource is one that is being (or can be) replenished as it is used. The uses of energy resources include: transport, electricity generation and heating. Students should be able to: describe the main energy sources available distinguish between energy resources that are renewable and energy resources that are non-renewable compare ways that different energy resources are used, the uses to include transport, electricity generation and heating understand why some energy resources are more reliable than others	WS 4.4
describe the environmental impact arising from the use of different energy resources	WS 1.3, 1.4
explain patterns and trends in the use of energy resources.	WS 3.5
Descriptions of how energy resources are used to generate electricity are not required.
Students should be able to: consider the environmental issues that may arise from the use of different energy resources show that science has the ability to identify environmental issues arising from the use of energy resources but not always the power to deal with the issues because of political, social, ethical or economic considerations.	WS 1.3, 1.4, 4.4 MS 1c, 2c, 4a

4.0 Subject content

4.2 Electricity