Energy: Need-to-Know Basics

Energy is the ability to do work or cause change, while work is the transfer of energy from one object to another or the transformation of energy from one form to another. For work to be done, there must be a force applied to an object over a distance. The amount of work done is equal to the force applied to the object multiplied by the distance over which the force is applied…

Work (Joules) = Force (Newtons) x Distance (metres)

For example, if you lift a box off the ground and onto a table, you are doing work on the box. The work you do on the box increases the potential energy of the box - the stored energy due to its position.

Calculating work done:

If you lift a box 1.5 metres using a force of 22 Newtons, the work you do on the box is:

Work = force x distance = 22 N x 1.5 m = 33 Joules

Energy can be stored in various ways, depending on the type of energy and the specific system or device being used. Here are some common ways that energy can be stored:

Gravitational potential energy: This is energy that is stored due to an object's position in a gravitational field. For example, a rock at the top of a hill has potential energy because it has the potential to do work (such as rolling down the hill) if it is released.

Elastic potential energy: This is energy that is stored in an object due to its deformation. For example, a stretched rubber band has potential energy that can be released when it is allowed to contract.

Thermal energy: This is energy that is stored in the movement of particles within a substance. The faster the particles are moving, the more thermal energy the substance has. For example, a pot of boiling water has more thermal energy than a pot of cold water.

Electrical energy: This is energy that is stored in the movement of electrons within a conductor, such as a battery or a capacitor.

Chemical energy: This is energy that is stored in the bonds between atoms in a substance. For example, gasoline has a lot of chemical energy stored in its molecules, which can be released when it is burned.

Magnetic energy: This is energy that is stored in a magnetic field. For example, an electromagnet has stored energy in its magnetic field.

Kinetic energy: This is energy that is stored in the motion of an object. For example, a moving car has kinetic energy due to its speed and mass.

The First Law of Thermodynamics, also known as the Law of Conservation of Energy, states that energy cannot be created or destroyed, only converted from one form to another. This means that the total amount of energy in a closed system is constant.

As an example, a car engine converts chemical energy stored in petrol or diesel into kinetic energy (the energy of motion) to move the car. According to the First Law of Thermodynamics, the total amount of energy in the system (the car and its engine) is constant, so the energy gained by the car in the form of kinetic energy must be equal to the energy lost by the engine in the form of heat and other forms of energy.

Energy always flows from a hotter body to a cooler body - this is the Second Law of Thermodynamics. As energy is transferred or transformed, some of it is always lost as heat. This means that it’s impossible to convert all the energy from one form to another with 100% efficiency – there will always be ‘wasted energy’.

Using the previous example of a car. According to the Second Law, some of the energy will be lost as heat, and the engine will never be able to convert all the energy from the fuel into useful work with 100% efficiency.

Key points about energy:

Energy is the ability to do work or cause change. It can be transferred from one object to another or transformed from one form to another.

There are different types of energy, including kinetic energy (the energy of motion), potential energy (the energy of position or configuration), thermal energy (the energy of temperature), electrical energy (the energy of moving electrons), and chemical energy (the energy stored in the bonds between atoms).

Work done is equal to the force applied to the object multiplied by the distance over which the force is applied… W = Fd.

The First Law of Thermodynamics states that energy cannot be created or destroyed, only converted from one form to another. This means that the total amount of energy in a closed system is constant.

The Second Law of Thermodynamics states that energy always flows from a hotter body to a cooler body, and as energy is transferred or transformed, some of it is always lost as heat. This means that it is impossible to convert all the energy from one form to another with 100% efficiency.