Tipos Abstractos de Datos Genéricos

B E H A V I O R

Air filters remove much of the particulate load in the air, keeping it out of the engine. Dirt in the air could clog small openings in the engine, restricting the flow of air or abrading parts.

H A B I TAT

Air filters sit directly above the engine.

H O W I T WO R K S

Most air filters today are made of resin-impregnated paper supported by a rim of plastic with a urethane gasket. The paper is folded or pleated to create a large surface area. Some filter elements have dimples to further increase the surface area so more particles are arrested. Incoming air has to travel through many sheets of paper before entering the engine’s intake valves.

Older cars used oil bath filters. In these filters, larger particles are thrown into the oil bath where they are trapped. The oil bath needs to be changed periodically. Smaller particles are caught in a fibrous material that surrounds the oil bath.

I N T E R E S T I N G FA C T

For every gallon of gasoline consumed about 10,000 gallons of air are sucked through an air filter.

Alternator

B E H A V I O R

It converts mechanical energy that the engine produces into alternat- ing current to run the car’s electrical system. Older cars had generators that produced direct current and filled the same role.

H A B I TAT

It is found on the side of the engine. A rubber belt from the crankshaft pulley turns the alternator.

H O W I T WO R K S

Alternators make alternating current (AC) by spinning a magnetic field. Coils of conducting wire surround the spinning magnets. Electrical cur- rent is inducted in the coils as the magnets spin. The direction of the current changes during every rotation of the magnets to produce AC.

Alternators replaced generators because they can be made stronger, lighter, and less expensive. They are easier to turn than generators and have a smaller pulley so they spin two to three times faster than the engine itself. (The pulleys and belt operate as a gear system that speeds up the rotation of the alternator.)

To charge the battery, current from the alternator is converted into direct current. A diode rectifier does this by limiting the direction the current can flow. The advent of solid-state diodes in the 1960s allowed the transition from generators to alternators. A voltage regulator con- trols the generator of electric power.

When you turn the ignition key the battery light comes on. The light is part of a circuit that sends a current to the alternator windings to start the magnetic field. As you turn the engine on it spins the alter- nator, which now generates electricity. But if the light remains on, it is indicating that the alternator isn’t producing enough electric power. It could be that the belt that turns the alternator has broken or that the

alternator itself is failing. Of course the car will still run, but you might notice that your headlights get progressively dimmer. Once you stop the car you probably won’t be able to restart it, as the battery will be dead. Under normal operations the light on the dashboard goes out after a few seconds. As the alternator starts generating electric power, it sends an opposing current to the light in the dash causing it to go out.

I N T E R E S T I N G FA C T S

The switch from using generators in cars to using alternators came about in the 1960s when solid-state diodes could be produced inexpensively. Diodes are needed to rectify the alternating current into direct current to charge the battery. With cheap diodes available, car manufacturers switched to the less expensive and more durable alternators.

Battery

B E H A V I O R

They provide the cup of Joe in the morning to start the car. Batteries store chemical energy and convert it into electric energy to power the starter and the many electrical appliances in a car.

H A B I TAT

In most American-made cars, batteries reside under the hood at a high level so they are accessible.

H O W I T WO R K S

Most car batteries are lead-acid, wet cell batteries. The cells are con- tained inside a polypropylene case.

The battery has six cells inside, each of which generates about two volts of electricity. The six cells are connected in series to yield 12+ volts. In a series circuit, the negative terminal of one cell is connected to the positive terminal of the adjacent cell and the voltages of each cell are added together to give the total voltage of the battery.

The cells have plates that serve as electrodes. The plates are made of lead and lead oxide and they are immersed in a bath of diluted (36 percent) sulfuric acid.

When the battery is discharging a chemical reaction occurs that con- verts lead and lead oxide into lead sulfate and releases electrons that

comprise electrical current. When the battery is charging (from the alternator) this chemical reaction is reversed so the lead sulfate becomes lead (at the negative electrode or plate) and lead oxide (at the positive electrode).

The positive terminal of the battery is connected to the starter motor. The negative terminal is connected to the car frame with a large wire. The ignition switch completes the circuit and powers the starter. Jump-starting the car is in essence connecting in parallel the dead battery to a battery in an operating car. Thus, the working car’s battery powers the other car’s starter. It’s important to know that the negative side of the battery connects to the frame. Touching the positive con- nection of the live battery to the frame will cause sparks to fly.

Most electric cars use the same lead-acid batteries that gasoline- powered cars use. However, they use many batteries instead of one. The lighter-weight alternative to a lead-acid battery is a nickel metal hydride battery.

I N T E R E S T I N G FA C T S

Before “maintenance-free” batteries, checking the water level in your battery was part of the car maintenance ritual. Now you never add fluid to the battery. Improved design for batteries reduces the loss of water. And solid-state electronic controls to prevent overcharging of the battery further reduce the loss of water.

Brake Cylinder (or