Capacitors

Ever wondered what a capacitor is and what it is used for?
A capacitor is simply two conductors that are separated by an insulator. The two conductors usually carry an equal and opposite charge such that total charge on the capacitor as a whole is zero. A capacitor is an electrical device that stores electric charge.
 
Charging and discharging a capacitor
Let's imagine a capacitor with two plates A and B. When a capacitor is connected to a battery, electrons flow from the negative pole of the battery on to plate A of the capacitor. At the same rate, electrons flow from the plate B of the capacitor towards the positive terminal of the battery. Positive and negative charges thus appear on the  plates. As the charges accumulates, the potential difference between A and B increases and the charging current reduces to zero when the potential difference becomes equal to the battery voltage.
When the battery is disconnected, the capacitor stays fully charged. To discharge the capacitor, the plates are joined with a thick wire and electrons flow from plate A to plate B until the positive charge on B is completely neutralized. A current thus flows for a time in the wire and at the end of time, the  charges on the plate becomes zero.
The ability of the capacitor to store charge is called the capacitance of capacitor and the unit is farad.

Uses of capacitor
Capacitors have many uses in electrical circuits. They are,
- Tuning in radio circuits
- Smoothening rectified current from DC suppliers
- Elimination of sparking in switches
- Storage of large quantities of charge
- Blocking of noise in an ac amplifier

A spark plug

A spark plug is what gives the cold fuel its hot behaviour and the energy to force the piston downward. It generates the electrical spark to ignite the fuel. The battery supplies the energy which is intensified by the ignition coils. The spark plug generates the spark by forcing the electrical charge to jump a gap in the lower part of the plug which is inside the cylinder.
To enable a spark to jump the gap, enough quantity of voltage must be made available by the ignition system.
In case you don't know, you can only find a spark plug in a petrol engine.

How a camera works

The simple camera is similar is in principle to the human eye. The camera is used in taking photographs of an object or a view. It is made up of a light proof box with a converging lens in front and and a light sensitive film at the back. A provision is made for adjusting the distance between the lens and the film, so objects in front of the lens can always be focused on the film by the converging lens. A better image can be formed by replacing the converging lens by different lenses.
A shutter of variable speed between the lens and the film shutts off light from the film and a diaphragm regulates the size of an aperture which controls the amount of light energy going into the film.
In taking a photograph, the camera is pointed at the object and the focusing ring is used to adjust the distance of the lens from the film until a sharp image is formed on the film. When a button is pressed, the shutter quickly opens and closes, exposing the film, for a brief period to light from the object. After the photograph is taken, the film is wound in between the spools.  

How a break system works

A brake is a device used for stopping moving vehicle.
The hydraulic brake is an arrangement which uses break fluid containing ethylene glycol to transfer pressure from the master cylinder to the slave cylinders at each wheel.
Car brakes use the hydraulic principle to to transmit pressure from the foot pedal to the brake. The foot brake of a car operates like a hydraulic press. The movement of the foot pedal operates a piston in the master cylinder and a hydraulic fluid transmits the pressure to slave cylinders which operates the brakes at each wheel. By properly calculating the diameters of the master and slave cylinders, the correct force can be obtained on the brakes of the wheels.
However, it is important in a car braking system that no air should enter the pipe containing the hydraulic fluid. Air unlike liquids, can be compressed, so with air present the brakes will not work properly.

How an alternator works

Ever wondered how an alternator works?
An alternator is a device that converts mechanical energy to electrical energy in form of AC current.
The alternator is what supplies the whole car with electricity. Did you think it was the battery? No. The job the battery does is to start the engine. Once the engine starts, the alternator takes over from the battery.
Electricity is produced in an alternator through electromagnetic induction.
The alternator has 3 main parts.
- stator : it is a stationary part in the alternator in which the rotor revolves, it consist of copper wires.
- rotor : it is the moving part of the alternator, it is like a long rod coated with magnet.
- Diode : it converts the AC current generated by the alternator to a DC current that can be used by the car.
When the alternator belt rotates the pulley on the alternator, the rotor which is made of magnet rotates very fast inside the stator and electricity is produced.
The alternator helps the engine by providing electricity for the spark plugs and the engine helps the alternator by rotating it.

How a jet engine works

Ever wondered how a jet engine operates?
A jet engine works according to Newtons third law of motion : for every action, there is equal and opposite reaction.
A jet engine creates forward thrust by taking in large amount of air and discharging it at a high speed jet of gases.

- air is drawn into the engine by a fan located in front of the engine
- the air is drawn into the compressor which has blade like wings and spins fast and thereby makes it a high pressure gas
- fuel is injected into the gas and ignited
- the burning gas expand and blast out through the nozzle at the back of the engine.
The hot air leaving the engine is twice the speed of cold air entering it at the front.