Conservation of Energy

The Principle of Conservation of Energy

As part of the BGE Science course, sources and types of Energy were covered. The main outcome can be shown in the following statement :-

'Energy cannot be created or destroyed, only changed from one form into another.' 

Types of Energy 

There are several types of Energy that are relevant to the National 5 course:-

1. Kinetic (movement) Energy.

2. Gravitational Potential Energy.

3. Light Energy.

4. Heat Energy.

5. Sound Energy.

6. Electrical Energy.

7. Chemical Potential Energy.

8. Nuclear Energy.

Energy Transformations

As stated above, Energy can only be changed from one form into another. Below are several examples of these Energy transformations:-

Energy Efficiency

All real-life systems waste energy in some way, they are not 100% efficient. Most of the waste energy is in the form of Light, Heat or Sound. 

For example - 

A  light bulb is designed to light a room. However, a traditional light bulb works by passing a Current through wire with a high Resistance until it heats up enough to glow, giving out light. This heat Energy is not useful to the system and is 'lost' to the environment. The more wasted Energy, the lower the efficiency of a system. 

The efficiency of a system can be found using the following formulae:-

Example 1 - 

A light bulb uses 100 J of Energy every second. If the light bulb gives out 70 J of heat Energy and 30 J of light Energy every second, what is the efficiency of the bulb? 

Efficiency  =  ( Eout / Ein ) x 100 

Efficiency  =  ( 30 / 100 ) x 100 

Efficiency  =  30 %


Example 2 - 

If an electric heater has an efficiency of 75% and gives out 3000 J of heat Energy every second, what is the total energy used per second?

Efficiency  =  ( Eout / Ein ) x 100 

Ein  =  ( Eout / Efficiency ) x 100 

Ein  =  4000 J every second