ENERGY SOURCES

WHAT ARE ENERGY SOURCES?
They are natural resources that we can use to generate different forms of energy. Then we can transform that energy for various purposes.

There are two types of energy sources: renewable and non-renewable.

NON-RENEWABLE ENERGY SOURCES
They come from natural resources that are limited. It would take millions of years to generate these sources of energy. The most commonly are fossil fuels (oil,coal and natural gas) and nuclear energy (radioactive materials)

RENEWABLE ENERGY SOURCES
They comme from natural resources that we can´t set up completly. These include hydroelectric, solar, marine, geothermal, and biomass.

ENERGY TRANSFORMATIONS
There are various types of energy transformations. We can transform chemical energy into other types of energy: 
1.Luminous energy  3.Sound energy
2.Thermal energy    4.Mechanical energy

We can transform electrical energy into:
1.Kinetic energy
2.Heat

We can transform nuclear energy into:
1.Luminous energy
2.Thermal energy

We can transform luminous energy into electrical energy.

ENERGY

WHAT IS ENERGY?
Energy is the capacity of a body to perform transformations and do works. It is measured in joules (J) and if it takes the form of heat, is measured in calories (cal).

FORMS OF ENERGY
There are many types of energy:
Potential- Energy that is stored and waiting to be used later.
Kinectic-The enrgy of physical movement
Mechanical-The sum of kinetic and potential energy
Sound-The energy of sound waves, wich are produced by vibrations.
Electrical-The product of an electrical current
Nuclear-The energy in the nucleus of an atom
Luminous-Associated with light 
Calorific-Associated with the movement of particles in matter
Chemical-Results from the formation or decomposition of substances.
Electromagnetic-Occurs when electrical currents create magnetic fields.

POWER
The power of a machine is the quantity of work that it can do in a certain amount of time. The I.S unit for power is the watt (W). 

🙌ENERGY🙌

1. What is the difference between a form of energy and an energy source?

Energy sources are used to generate different forms of energy. For example: we use luminous energy to generate electrical energy.

2. Can you name an energy source?

Fossil fuel.

3. What is a renewable energy source?

Renewable energy come from natural resources but we can't use up completly, and we can get them with special machines.

4. Where do oil, gas and coal come from?

They come from fossil fuels, and fossil fuels come from natural resources.

5. What types of power stations do you know?

Thermal power station, nuclear power station, wind farms, hydroelectric power station, solar power station, biomass power station, marine power station and geothermalpower station.

6. How is electricity transported from a power station to your home?

Energy goes through high voltage lines, that are installed on towers and before that electricity arrive to your home, a substation transformer reduced the power to lover voltages.

7. What do "greenhouse effect" and "acid rain" mean? How are they related to energy production?

⇨Greenhouse effect: When we burn fossil fuels, gases are released into the air. These gases contribute to the greenhouse effect, wich increases the Earth's average temperature.

⇨Acid rain: Power stations that burn fossil fuels also release other pollution into the air. These pollutants combine with water vapour in the air to produce acid rain.

MECHANISMS THAT CONTROL MOTION

DIRECTION CONTROL: ratchets
A rachet is a mechanism that controls the direction of motion. It allows motion in one direction, but not in the other.

SPEED REDUCTION: brakes

Brakes use friction to reduce speed and they are activated by levers that transmit force to an output receptor, which put pressure on the wheel. This produces friction, and slow down the wheel.

There are various types of brakes according to where the friction is produced:

Disc brake

Band brake

Drum brake

⇨Disc brakes: A disc is connected to an axle. Brake pads apply pressure to the disc.

⇨Band brakes: A drum is connected to an axle. A flexible band applies pressure to the outside of the drum.

⇨Drum brakes: A drum is connected to the axle. A pair of brake shoes apply pressure to the inside of the drum.

  ⇒TRANSFORMATION OF MOTION⇐

ROTARY-LINEAR TRANSFORMATION

WHEEL

Wheels reduce contact with the ground and decrease friction. If there isn't enough friction, they can slide out of control. We need less force to move vehicles with larger wheels and they move more quickly.

RACK AND PINION

This mechanism has two parts: the rack is a bar with many theeth and the pinion is a gear with theeth that interlock with the rack. It transforms rotary motion into linear motion.

NUT AND BOLT

This mechanism transforms rotary motion into linear motion. It has two parts: a bolt with a spiral groove and a nut that turns around it.

WINCH AND CRANK
It is a cylinder that rotates around a horizontal axis. We turn the crank to rotate the winch. The crank increases the force and the winch transforms rotary motion into linear motion. This mechanism has the Law of the Lever.

RECIPROCATING ROTARY-LINEAR TRANSFORMATION

CRANKSHAFT

We can conect multiple rods to one shaft. The rods are connected to cranks, and the cranks are connected to the crankshaft. It can synchronise the movements of various parts.

CAM

A cam is a irregulary device that rotates on a shaft. When the cam rotates, it pushes a special bar called follower. This follower can move other parts or it can turn a switch on and off.

When we put multiple cams on a shaft, it's called a camshaft. We can use it to synchronise the movements of various parts.

ROTARY TRANSMISSION

Rotary transmission systems put two rotating elements into contact. These mechanisms have two purposes:
⇒Transferring rotary force to an input location to another location.
⇒Changing the rotary speed by using rotating elements of different sizes.
There are various mechanisms:

    

Pulleys with belts

Friction wheels

Interlocking gears

Sprockets with chains

 

Here, the most reliable mechanism is the interlocking gears, because they don't slip easily.

CHANGES IN SPEED

We can increase, decrease and make constant the speed with these systems:

  

Decreasing and  Increasing speed system

Cosntant speed system

SPEED RATIOS

The relationship between the speeds of the two wheels is inversely proportional to their sizes. 

                                      

                         N2/N1=D1/D2

The relationship is called the ratio of transmission, where N is the speed of relation and D is the diameter of the wheel. 

BELT DRIVES AND GEAR TRAINS  

-Wheel 1 turns wheel 2, wich moves faster because it is smaller. If wheel 1 makes 1 rotation, wheel 2 makes 1.5 rotations.

-Wheel 2 and wheel 3 are connected to the same axis, so they turn together.

-Wheel 3 turns wheel 4, wich moves faster because it is smaller. If wheel 3 makes 1.5 rotations, wheel 4 makes 3 rotations (1.5x2=3)

                      N4/N1=D1XD3/D2XD4

CHANGES IN DIRECTION AND ROTATIONS

We can change the direction of the rotation by using belts in different possicions or different axis.

Parallel axes

Perpendicular axes

Different posicion of the belts

Crossed axes

 








WORM DRIVE
A worm drive reduces the speed of rotary system very well. It has two parts: a worm shaft and a worm gear. The shaft has more than one groove. Each groove interlocks with one of the worm gear. This mechanism is not reversible.