GCSE Physics: Energy Stores and Systems Flashcards

Question 1

What is System?

Accepted Answer

An object or group of objects chosen for study, so that energy changes can be tracked as energy moves between the stores inside it and its surroundings.

Question 2

Define Closed System.

Accepted Answer

A system that no matter or energy can enter or leave, so its total energy stays fixed however much energy moves between the stores inside it.

Question 3

Define Energy Store.

Accepted Answer

A way of describing where energy is held in a system, such as kinetic, gravitational potential, elastic potential or thermal, with the amount in each store measured in joules.

Question 4

Define Kinetic Energy Store.

Accepted Answer

Energy held by anything that is moving; the amount depends on the object's mass and grows rapidly with speed, because speed enters the formula squared.

Question 5

Define Gravitational Potential Energy Store.

Accepted Answer

Energy an object has because of its position in a gravitational field; lifting the object higher does work against gravity and fills this store.

Question 6

Define Elastic Potential Energy Store.

Accepted Answer

Energy held in an object that has been stretched, compressed or bent, which can be fully recovered only if it has not been deformed beyond its limit of proportionality.

Question 7

Define Thermal Energy Store.

Accepted Answer

Energy held by an object because of its temperature, carried in the motion and vibration of its particles; heating the object raises the energy in this store.

Question 8

Define Chemical Energy Store.

Accepted Answer

Energy held in substances such as food, fuels and the chemicals in batteries, released when those substances react, for example during burning or respiration.

Question 9

Define Nuclear Energy Store.

Accepted Answer

Energy held inside the nuclei of atoms, released when nuclei split apart in fission or join together in fusion.

Question 10

Define Work Done by a Force.

Accepted Answer

Energy transferred when a force moves an object through a distance in the direction of the force, calculated as force in newtons multiplied by distance in metres.

Question 11

Define Electrical Work.

Accepted Answer

Energy transferred when an electric current flows, as charge moving round a circuit carries energy from the power supply to the components.

Question 12

What is Heating?

Accepted Answer

The transfer of energy from a hotter object to a cooler one because of their temperature difference, raising the energy in the cooler object's thermal store.

Question 13

Define Transfer by Radiation.

Accepted Answer

The transfer of energy by electromagnetic waves such as light and infrared, which need no material to travel through and so can cross the vacuum of space.

Question 14

Define Conservation of Energy.

Accepted Answer

The law that energy can be transferred usefully, stored or dissipated but can never be created or destroyed, so the total before any change equals the total after.

Question 15

What is Dissipation?

Accepted Answer

The spreading out of energy into stores where it is less useful, usually the thermal store of the surroundings, so it can no longer do useful work; often called wasted energy.

Question 16

Define Useful Energy.

Accepted Answer

Energy transferred to the store a device is designed to fill, such as the kinetic store of a motor's shaft or the light given out by a lamp.

Question 17

What is Efficiency?

Accepted Answer

The fraction of the total energy supplied to a device that is transferred usefully, given as a decimal or percentage, and never greater than 1 or 100%.

Question 18

What is Power?

Accepted Answer

The rate at which energy is transferred or work is done, measured in watts, where one watt means one joule of energy transferred every second.

Question 19

What is Joule?

Accepted Answer

The unit of energy and of work done; one joule is the work done when a force of one newton moves an object through one metre.

Question 20

Define Kinetic Energy Equation (Ek = ½mv²).

Accepted Answer

The formula for the energy in a moving object's kinetic store: one half of its mass in kilograms multiplied by the square of its speed in metres per second.

Question 21

Define Gravitational Potential Energy Equation (Ep = mgh).

Accepted Answer

The formula for energy gained in a gravitational potential store: mass in kilograms times gravitational field strength in newtons per kilogram times change in height in metres.

Question 22

Define Elastic Potential Energy Equation (Ee = ½ke²).

Accepted Answer

The formula for energy in a stretched spring: one half of the spring constant in newtons per metre times the extension in metres squared, valid up to the limit of proportionality.

Question 23

Define Spring Constant.

Accepted Answer

A measure of a spring's stiffness, equal to the force needed to stretch it by one metre, in newtons per metre; a stiffer spring has a larger spring constant.

Question 24

What is Extension?

Accepted Answer

The increase in length of a spring or elastic object compared with its original, unstretched length, written in metres when used in energy calculations.

Question 25

Define Gravitational Field Strength.

Accepted Answer

The force of gravity acting on each kilogram of mass, measured in newtons per kilogram; at Earth's surface it is about 9.8 N/kg.

Question 26

Define Specific Heat Capacity.

Accepted Answer

The amount of energy needed to raise the temperature of one kilogram of a substance by one degree Celsius, measured in joules per kilogram per degree Celsius.

Question 27

Define Change in Thermal Energy Equation (ΔE = mcΔθ).

Accepted Answer

The formula for the energy needed to change a material's temperature: mass in kilograms times specific heat capacity times temperature change in degrees Celsius.

Question 28

Define Thermal Conductivity.

Accepted Answer

A property of a material describing how readily energy passes through it by conduction; the higher it is, the higher the rate of energy transfer through the material.

Question 29

Define Thermal Insulation.

Accepted Answer

A material with low thermal conductivity used to reduce unwanted energy transfer by heating, so hot objects stay hot and cold objects stay cold for longer.

Question 30

What is Lubrication?

Accepted Answer

Adding a substance such as oil or grease between moving surfaces to reduce friction, so less energy is dissipated by heating and the machine becomes more efficient.

Question 31

Define Rate of Cooling of a Building.

Accepted Answer

How quickly a building loses energy to colder surroundings; thicker walls and wall materials with lower thermal conductivity make the rate lower, so the building cools more slowly.

Question 32

Define Sankey Diagram.

Accepted Answer

A diagram showing the energy transfers in a device as arrows whose widths are drawn to scale, so useful and wasted outputs can be compared at a glance.

Question 33

Define Renewable Energy Resource.

Accepted Answer

An energy resource that is being, or can be, replenished as it is used, such as wind, hydro-electricity, the tides, water waves, geothermal, the Sun and bio-fuel.

Question 34

Define Non-Renewable Energy Resource.

Accepted Answer

An energy resource that will run out because it is used far faster than it can be replaced, such as coal, oil, gas and nuclear fuel.