3. SIMPLE MACHINES :SIMPLE MACHINES :
Simple machine is a device in which effort is applied at one place
and the work is done at some other place.
Simple machines are run manually, not by electric power.
e.g. - Inclined Plane
- Screw
- Lever- Lever
- Pulley
- Simple Screw Jack, etc.
5. 1. Inclined Plane :
An inclined plane is a flat surface that is higher on one end.
You can use this simple machine to move an object to a
lower place or higher place.
Inclined planes makes the work of moving things easier. You
would need less energy and force to move objects through Inclined
plane.
Examples of Inclined Plane :
1. Ramp
2. Slanted Road
3. Path Up a Hill
4. Slide
6. 2. The Screw :
The screw is a simple machine made from another simple machine.
It actually is an inclined plane that winds around itself.
A Screw has ridges and is not smooth like a nail. Some Screws are used
to lower and raise the things. Some screws are also used to hold things
together.
Examples of the Screw :Examples of the Screw :
1. Jar Lids
2. Light Bulbs
3. Stools
4. Clamps
5. Jacks
6. Spiral Staircase
7. Wrentches
8. Key Rings
7. 3. Lever :
A lever is a broad or a bar that rests on a turning point. This turning
point is called fulcrum.
The object that the lever moves is called the load. The closer the object
is to the fulcrum the more easier it is to move the object.
Examples of the Lever :
1. A Hammer is a lever used to pull out nail of wood.
2. Bottle openers2. Bottle openers
3. Crow bars
8. 4. Pulley:
This simple machines is made up of a wheel and a rope. The rope fits in
the groove of the wheel.
One part of the rope is attached with the load. When you pull on one
side of the pulley, the wheel turns and the load will move.
Pulley lets you move load up, down, or sideways. Pulleys are too good
for moving objects to hard to reach the places. It also makes the work
of moving heavy loads much easier.
Examples of Pulley :
1. Flag poles
2. Clothes lines
3. Sail boats
4. Blinds
5. Cranes
9. ELECTRIC MACHINES :ELECTRIC MACHINES :
•An electrical machine is the apparatus that converts energy in three
categories:
1. Generators which convert mechanical energy to electrical
energy,
2. Motors which convert electrical energy to mechanical energy,
and
3. Transformers which changes the voltage level of an alternating
current.current.
10. Generators
AC Generators
Motors
AC Motors
Transformers
Step-up Transformers
The three apparatus can be further classified into other two parts based
on the properties and characteristics of their work, as under:
DC Generators DC Motors
Step- down
Transformers
13. 1. Mechanical Advantage (MA) :
The ratio of load lifted (W) and effort
required (P) is called Mechanical Advantage.
2. Velocity Ratio (VR) :
The ratio of distance moved by the effort and
The distance moved by load is called Velocity Ratio.The distance moved by load is called Velocity Ratio.
3. Input :
Input = effort × distance moved by the effort
14. 4. Output :
Output = load × distance moved by the load
5. Efficiency :
The ratio of work done by the machine and work
done on the machine is called efficiency of the machine.
15. 6. Ideal Machine :
A Machine having 100% efficiency is called an Ideal Machine.
In an Ideal Machine, friction is zero.
For Ideal Machine,
Output = Input
or
MA = VR
7. Effort Lost in Friction :
In a Simple machine, effort required to overcome the friction between
various parts of the machine is called effort lost in friction.various parts of the machine is called effort lost in friction.
16. 8. Reversible Machine :
If a machine is capable of doing some work in the reverse direction, after
the effort is removed, is called reversible machine.
For reversible machine, Efficiency => 50%
9. Non-reversible Machine or self-locking machine:
If a machine is not capable of doing some work in the reverse direction,
after the effort is removed, is called non-reversible machine or
self-locking machine.
For non-reversible machines, Efficiency < 50%
