Machines are used to perform all types of work by applying small effort at one end of the machine to overcome a load at another end. In the last presentation, I explained what mechanical advantage of machines are and demonstrated how to calculate it. Another property of machines is efficiency and we want to understand what it is all about.
Understanding Efficiency
When a load is supplied to a machine, it is effected to overcome the load by the application of some force or energy. The efficiency of any machine describes how well it utilizes the force to overcome the load. If a machine is 100% efficient, it means that it used the entire force applied to overcome the load. Most times, this is not possible as some of the force applied is lost through some events like heat and friction.
However, the efficiency of a machine which is usually measure in percentages should be as close to 100% as possible. The higher the efficiency of any machine, the better it accomplishes the work it was intended to perform. There are many reasons why the entire force of a machine is not always used to overcome the load. Here are some reasons.
Friction: When two surfaces move against each other, there is a force that opposes their movement. This force is called friction. Friction is mostly felt when two metallic surfaces grind against each other. The force of friction converts some of the mechanical energy into heat energy. This is usually the reason why you observe several sparks when one metal surface grinds against another one. The force of friction produces heat from the mechanical energy. As a result the entire force produced by the machine is not used to perform work.
Air resistance: As objects move through space, they encounter some pull back or drag caused by the air. This drag is often called air resistance. Consider a vehicle speeding along a high way. The entire forward force produced by the engine are not used entirely to move forward. As the vehicle speeds through the road, the air in front of it and by the sides drag it back by a small margin. This air resistance thereby converts some of the mechanical energy and thereby prevents the vehicle from entirely using its engine force to move.
Electrical resistance: Some machines have components that are wired. These electrical components transfer energy from one part of the machine to another. This movement of electrical energy from one component to another generates some heat. The heat generated is from the force produced by the machine. Because of this conversion of mechanical energy to electrical energy, the machine looses some force and is not 100% efficient.
Consider an electrical motor with positive and negative wires inside it. As these components come together, they produce some sparks. These sparks are physical evidence of loss of mechanical energy in forms of light and heat. It prevents the machine from completely using the energy it produced to overcome load as some of it is lost within the electrical components in the machine.
Improving efficiency through lubrication
Many machines contain metal surfaces and parts that move against each other to perform work. This is why friction is the most popular form of energy loss in machines. In order to reduce friction and hence improve efficiency of machines, lubricants are used.
Lubricants are usually oil liquids that are applied to moving parts and metallic surfaces of machines in order to reduce loss of heat through friction. While this is very important, it does not guarantee 100% efficiency of the machine. But it greatly improves efficiency and also reduces the wear and tear that happens to metallic parts of machines.
Finally
No machine is 100% efficient. But each machine should be as close to 100% as possible. A machine that looses large amounts of its energy is never so efficient and that affects the amount of work it will be able to do. If you work with a machine that has metal moving parts, always apply enough lubricants to help the machine improve its efficiency.
Reference
https://www.school-for-champions.com/machines/efficiency.htm