Energy Concepts

Flashcards covering energy stores, calculations, transfers, resources, and environmental impact.

System

An object or group of objects.

Kinetic Energy Transfer (Example)

Energy transferred as sound when a moving ball hits a wall.

Vehicle Slowing Down (Energy Transfer)

Energy transfers to thermal energy due to friction.

Kinetic Energy Formula

1/2 * mass * speed^2

m (Kinetic Energy Formula)

Kilograms (kg)

v (Kinetic Energy Formula)

Metres per second (m/s)

Ek (Kinetic Energy Formula)

Joules (J)

Elastic Potential Energy

The type of energy stored in a spring when it is stretched

Elastic Potential Energy Formula

1/2 * spring constant * extension^2

Ee (Elastic Potential Energy Formula)

Elastic potential energy, in joules (J)

k (Elastic Potential Energy Formula)

Spring constant, in newtons per metre (N/m)

e (Elastic Potential Energy Formula)

Extension in metres (m)

Gravitational Potential Energy Formula

mass * gravitational field strength * height

Ep (Gravitational Potential Energy Formula)

Gravitational potential energy, in Joules (J)

g (Gravitational Potential Energy Formula)

Gravitational field strength (9.8 m/s^2), in newtons per kilogram (N/kg)

h (Gravitational Potential Energy Formula)

Height in metres (m)

Specific Heat Capacity

The energy required to raise the temperature of 1kg of a substance by 1°C or 1K

Energy (Specific Heat Capacity) Formula

mass × specific heat capacity × temperature change

∆E (Specific Heat Capacity Formula)

Change in thermal energy, in joules (J)

m (Specific Heat Capacity Formula)

Mass, in kilograms (kg)

c (Specific Heat Capacity Formula)

Specific heat capacity, in joules per kilogram per degree Celsius (Jkg−1°C−1)

∆T (Specific Heat Capacity Formula)

Temperature change in degrees Celsius (°C)

Power

The rate at which energy is transferred or the rate at which work is done.

Power Formula

energy transferred / time = work done / time

P (Power Formula)

Power, in watts (W)

E (Power Formula)

Energy transferred, in joules (J)

t (Power Formula)

Time, in seconds (s)

W (Power Formula)

Work done, in joules (J)

Energy Conservation

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

Energy Dissipation

In all system changes energy is dissipated, so that it is stored in less useful ways.

Lubrication

Reduces friction, so less energy is lost (as heat) through friction.

Thermal Insulation

Less useful thermal energy lost.

Thermal Conductivity

The higher the thermal conductivity of a material, heat is allowed to travel through the material more easily, so the higher the rate of energy transfer by conduction across the material.

Thermal Conductivity in Buildings

Rate of cooling is low if walls are thick and thermal conductivity of the walls are low.

Efficiency

The ratio of the useful work done by a machine, engine, device, etc, to the energy supplied to it, often expressed as a percentage.

Efficiency Formula

useful energy output / total energy input = useful power output / total power input

Increasing System Efficiency

Reducing waste output (lubrication, thermal insulation, etc.) Recycling waste output (e.g. absorbing thermal waste and recycling as input energy)

Non-Renewable Energy Sources

Fossil Fuels (coal, oil, gas) Nuclear Fuel

Renewable Energy Sources

Biofuel, Wind, Hydro-electricity, Geothermal, Tidal, Solar, Water waves

Renewable Energy

Energy which can be replenished as it is used.

Non-Renewable Energy Use

Is used more for large-scale energy supplies due to the large energy output per kilogram of fuel – renewable resources cannot provide such a large amount of energy as easily.

Renewable Energy Reliability

Solar doesn’t work in bad weather or night, wind is only intermittent.

Main Energy Uses

Transport, Electricity generation, Heating

Extraction of Energy (Environmental Impact)

Fossil fuels involve destroying landscapes, wind turbines can be considered an eyesore

Use of Energy Sources (Environmental Impact)

Fossil fuels release harmful emissions, solar, wind directly create electricity with no emissions