AQA Physics: Unit 1- Energy

Comprehensive practice flashcards covering AQA GCSE Physics topics P1a (Energy stores and transfers), P1b (Heat transfers), and P1c (Energy resources), including key definitions, equations, units, experiments, and environmental impacts.

What is the scientific definition of a system?

An object or a group of objects.

What is an energy store, and what are the eight examples of energy stores?

If a system has a store of energy, it has the ability to do work. Energy stores can increase or decrease when transfers occur and are measured in joules ($\text{J}$). The eight examples are kinetic (moving), thermal, gravitational potential, elastic potential, magnetic, electrostatic, nuclear, and chemical.

What is an energy transfer, and what are the four main transfer pathways?

An energy transfer occurs when energy is moved from one energy store to another, measured in joules ($\text{J}$). The four pathways are mechanical (a force moving an object), work done by current (due to a voltage/potential difference), heating (due to temperature difference), and radiation (e.g. visible light, infra red).

What is work, and what is the equation used to calculate it?

Work is the amount of energy transferred when an object is moved over a distance by an external force. Word equation: $\text{work done} = \text{force} \times \text{distance}$; Symbol equation: $W = F\,s$.

What is the equation used to calculate gravitational potential energy ($E_p$)?

Word equation: $\text{gravitational potential energy} = \text{mass} \times \text{gravitational field strength} \times \text{height}$; Symbol equation: $E_p = m\,g\,h$.

What is the equation used to calculate kinetic energy ($E_k$)?

Word equation: $\text{kinetic energy} = 0.5 \times \text{mass} \times \text{speed}^2$; Symbol equation: $E_k = \frac{1}{2}\,m\,v^2$.

How is power defined, and what are the two equations used to calculate it?

Power is the rate at which energy is transferred or the rate at which work is done, measured in watts ($\text{W}$), where $1\,\text{W} = 1\,\text{J/s}$. The equations are $\text{power} = \frac{\text{energy transferred}}{\text{time}}$ ($P = \frac{E}{t}$) and $\text{power} = \frac{\text{work done}}{\text{time}}$ ($P = \frac{W}{t}$).

What is the definition and formula for energy efficiency?

The ratio of useful output energy transfer to total input energy transfer, written either as a decimal or a percentage. Formula: $\text{efficiency} = \frac{\text{useful output energy transfer}}{\text{total input energy transfer}} = \frac{\text{useful power output}}{\text{total power input}}$.

What is the equation for calculating elastic potential energy ($E_e$)?

Word equation: $\text{elastic potential energy} = 0.5 \times \text{spring constant} \times (\text{extension})^2$; Symbol equation: $E_e = \frac{1}{2}\,k\,e^2$.

What is specific heat capacity, and what is its unit of measurement?

The amount of energy required to increase the temperature of $1\,\text{kg}$ of a substance by $1\,^{\circ}\text{C}$. Its unit is joules per kilogram per degree Celsius ($\text{J/kg}\,^{\circ}\text{C}$).

What is the equation linking change in thermal energy, mass, specific heat capacity, and temperature change?

Word equation: $\text{change in thermal energy} = \text{mass} \times \text{specific heat capacity} \times \text{temperature change}$; Symbol equation: $\Delta E = m\,c\,\Delta \theta$.

What is the law of conservation of energy?

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

What is dissipated energy, and how can it be reduced?

Energy that has been transferred to a store that is not useful, sometimes referred to as "wasted" energy. It can be reduced with lubrication or thermal insulation.

What is conduction, and how does thermal conductivity influence energy transfer?

Conduction is a method of thermal energy transfer through the passing on of particle vibrations. The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material.

What factors reduce the rate of cooling of a house?

Houses have a slower rate of cooling if they have thicker walls. The rate of cooling can also be reduced by decreasing the thermal conductivity of the walls through installing cavity wall insulation.

How does this experimental setup investigate the thermal conductivity of different materials?

By heating the touching ends of rods made from different materials (iron, brass, copper, aluminium) with a Bunsen burner and timing how long it takes for drawing pins stuck with vaseline to drop off the other ends. The less time taken, the higher the thermal conductivity.

What is the difference between a non-renewable and a renewable energy resource?

A non-renewable energy resource cannot be replenished as it is used and will run out at some point. A renewable energy resource can be replenished as it is used and will not run out.

What are the three main uses of energy and the primary fuel sources used for each?

1. Transport: petrol, diesel, and kerosene produced from crude oil (used in cars, planes, and trains).
2. Heating: gas and electricity (used in buildings).
3. Electricity: mostly generated by fossil fuels (used to power most devices).

What daily and seasonal patterns characterize energy demand?

Daily changes: less energy is used at night, and more is used at tea time. Seasonal changes: more energy is used in winter as it is colder and darker.

How do fossil fuels generate electricity, and what are their reliability and environmental impacts?

Fossil fuels (coal, oil, and gas) are burnt to turn a turbine which turns a generator. They are very reliable. Positives: high energy density and provides most of the energy in the UK. Negatives: releases carbon dioxide which causes global warming, and releases sulphur dioxide which causes acid rain.

How does nuclear energy work, and what are its environmental impacts?

Nuclear fission is used to turn the generator. It is very reliable. Positives: no carbon dioxide is released and it has very high energy density. Negative: risk of harmful radioactive material being released in an accident.

How do biofuels work, and why are they considered carbon neutral?

Organic matter is burnt (fairly reliable). Biofuels are carbon neutral because carbon dioxide is released when burnt, but when a new plant grows it is taken back from the atmosphere. A negative impact is that large areas of land needed for crops cause habitat destruction.

How do geothermal and hydroelectric energy sources generate power, and what are their negative environmental impacts?

Geothermal uses hot magma to turn generators (very reliable; negative: only available in very few areas, small area of habitat destroyed). Hydroelectric uses falling water to turn the generator (usually reliable; negative: habitats destroyed when dams of large area are built).

Why are solar, wave, and wind energy considered "not reliable", and what are their environmental impacts?

They depend on variable natural conditions (sun, up and down water motion, wind). All release no carbon dioxide or sulphur dioxide during use. Negatives: carbon dioxide is released during the manufacturing of the devices/turbines; wind power additionally causes some visual and noise pollution.

How does tidal energy generate electricity, and what are its reliability and environmental impacts?

The rise and fall of tides turn generators. It is very reliable and releases no carbon dioxide or sulphur dioxide during use. Negatives: structures built across estuaries cause disruption to habitats, and some carbon dioxide is released in the making of the devices.