Without electrical current, you might as well remove your car's wheels and prop it up on concrete blocks on the lawn. Your car is an electrical machine, and the battery is what gives it life.

Most car batteries are of the lead-acid variety, and their primary job is to leap into action as soon as you turn the key in the ignition. This causes a weak electrical current to flow from the battery to asolenoid or relay — an electromagnetic switch that closes a circuit. The closed circuit lets the battery's full voltage flow to the starter motor.

The starter motor begins a process that turns the flywheel and the crankshaft and subsequently, the pistons. The pistons draw a combustible fuel/air mixture, a spark plug provides ignition and presto — your car's engine starts, and your battery's biggest task is, for the moment, complete.

Batteries contain chemicals and gases that can seep out and cause corrosion on battery terminals. Scrub your battery's terminals using an old toothbrush and a mixture of baking soda and water. This simple chore can prolong the battery's life and keep you from being stranded.

But the battery isn't just sitting idle as you drive down the highway. Next, you'll see the reward your battery gets for a job well done.

Your battery's primary purpose is to start your car. Once the engine is running, the crankshaft spins, and as it does, it transmits some of its mechanical energy through a belt to an alternator.

The alternator is hugely important. It provides power for every part of the vehicle once the car is started. The alternator also tops off the battery's charge, ensuring that the battery will be ready to start the car the next time you need it.

Like a lot of individual car parts, the alternator is a rather complicated doodad, and one that deserves a more thorough understanding. You can read more about it in our article How Alternators Work.

In short, your alternator is made up of coils of wires positioned around a spinning rod, which produces alternating current (AC) power through electromagnetism. The resulting electricity moves through wiring to power everything in the car, from the radio and onboard computers to all switches and sensors that make your car work.

One myth about alternators and dead batteries is that you can jump-start your car and drive it around for a while to recharge your dead battery. In modern cars, doing this very thing can actually overheat and damage (or destroy) your alternator. A standalone car battery charger is a much safer option.

Taking good care of your car's electrical system is important for maintaining a reliable vehicle. On the next page, you'll read about one of the more electrically sensitive parts of your car.

Modern cars are anything but a rolling collection of dumb, greasy gears. They contain sophisticated onboard computers, and the primary computer is thePCM (powertrain control module), a microprocessor that functions as the car's information overlord.

Without a properly functioning PCM (also sometimes called an ECU, or electronic control unit), the car as a whole doesn't work as efficiently as it should. In some cases, it may not run at all. The PCM controls and coordinates all of your car's functions, from the transmission, to emissions controls, to electrical and charging capabilities, to valve timing, idle speed, ignition timing and more.

The PCM receives data from sensors all over the car and uses that data to calibrate and balance all sorts of system capabilities. One of the PCM's most important functions is to calculate the best fuel flow rate required to sustain the correct air/fuel ratio in the engine.

These days, PCMs are incredibly advanced — for example, they can sense altitude, which affects fuel combustibility, and can adjust the fuel/air mixture automatically to maximize power and fuel efficiency. You can read even more about them in How Car Computers Work.

Now you know that the PCM keeps your car systems under control. But as you'll read on the next page, humans are still the real masters of a car's most difficult maneuvers.

The PCM is the electronic brains of your car. Thesteering column, however, helps connect the flesh-and-blood operator — you — to the car's primary functions.

The steering column is topped with the steering wheel, which of course lets you guide the car precisely down a highway at full speed, or to quickly dodge a deer that jumps out onto the road. But the steering column is also a hub for other important car controls.

On most vehicles, the steering column houses the ignition switch that lets you start the car. And many cars have a gear shifter on the steering column, too. This shifter lets you take the car out of park and get moving, in either forward or reverse.

Controls for other necessities often sprout from the steering column; notably, the toggle switches for the headlights and windshield wipers. With these controls in easy reach, you can quickly adapt to low light and inclement weather conditions.

Many steering columns are made to be collapsible in the event of a head-on collision. These columns disperse the impact's energy and crumple to prevent the steering wheel from crushing the driver.

Now that you know the human brain is still the most important asset you have in operating a vehicle safely and reliably, we'll dive back under the hood to investigate other paramount car parts.

Most cars require fossil fuels in the form of gasoline in order to get you moving down the road. But liquid gas doesn't burn – it's the fuel vapors that are combustible. In order to make the liquid gas in your fuel tank usable, your car needs fuel injectors.

A fuel pump pushes gas from the tank, through a fuel filter that removes any debris or dirt, and towards the engine's fuel rails, which house the fuel injectors. As the fuel pump works, it also pressurizes the liquid, forcing it into the injectors.

The fuel injectors have a spray tip that atomizes the liquid fuel and disperses it into the engine's airstream. The resulting air/fuel mixture is high combustible. Spark plugs ignite this blend of gas and air, creating controlled explosions that push the pistons, which turn the crankshaft and propel the car.

Sometimes fuel injectors become dirty or blocked, resulting in inconsistent spray. As a result, the engine works harder and less efficiently. In some cases, the PCM will overcompensate for the low fuel flow by trying to force even more gas into the injectors, beginning a chain reaction that can overstrain the motor and cause total failure. You can find out more about this system in How Fuel Injector Systems Work.

Fuel injectors, however, are pretty dependable and don't account for too many problems on the road. Our next system, though, fails more often than we'd like to admit and sometimes strands drivers on the shoulder of the road calling for help.

By their very nature, internal combustion engines run hot. To understand that, all you have to do is touch the hood of your car after a long drive. But the heat your engine generates is also one of its worst enemies, and if it spikes to high levels, the engine can destroy itself. That's where the cooling systemcomes in.

All modern engines use a liquid-cooling system. Awater pump pushes engine coolant through passages in the motor. As the coolant travels, it absorbs heat from the engine, and takes that heat to the radiator, a block of aluminum tubes that disperse heat to surrounding air.

A thermostat regulates coolant flow. If the engine is running too cool, the thermostat blocks the coolant from reaching the radiator, causing the coolant liquid to remain in the engine block. Once the coolant reaches the correct operating temperature (around 190 degrees Fahrenheit / 88 degrees Celsius) the thermostat opens and lets the coolant flow through the radiator again.

Engine coolant, like air, tends to rise when it gets hot. That's why almost all cooling systems flow upwards through the engine.

There's a lot more to know about cooling systems. You can read more about them in How Car Cooling Systems Work.

Cooling systems are really pretty simple, and they work well — unless you forget to add coolant, of course. Our next car system, however, is anything but simple.

In terms of mechanical complexity, nothing else in your car can compare to the transmission. The transmission is also imperative to your car's performance.

The transmission performs an essential task. It transfers the energy of the crankshaft's rotation to a system of gears that turns the wheels. If that sounds pretty simple, well, it's not. But if you want more details on transmissions, read How Automatic Transmissions Work or How Manual Transmissions Work.

Modern transmissions, whether they're manual or automatic, are incredibly complicated. They depend upon a whole range of mechanical, hydraulic, and electrical systems, all operating within precise parameters that keep your car operating safely and efficiently. A car's computer orchestrates all transmission-related functions.

Your engine runs best within a certain (and rather narrow) speed range. But to drive on slow, city streets and wide-open highways, you need to be able to make the car go slower or faster without damaging the engine.

A single gear, then, doesn't cut it. The various gears in your transmission let you speed up and slow down, without causing drastic (and damaging) speed fluctuations in the engine itself. Lower gears spin faster to generate more power and keep the car moving at slow speeds or on hills. Higher gears help the engine run more slowly as you zoom along at highway speeds and flat sections of road.

Because transmissions are so complicated, when they fail, they're usually very expensive to fix. This system contains many pumps, cables, gears, valves and gaskets. So finding and repairing the problem is time-consuming and often requires the attention of a transmission specialist.

Not all car components are so wildly complicated. Keep reading and you'll see another indispensable piece of your vehicle.

Some brand-new highways are smooth, flat testaments to engineering ingenuity. Others are pothole-riddled, patchwork monstrosities that jolt cars and trucks (and their human contents) and make them lurch all over the road. It's no wonder, then, that a good suspension system is indispensable.

Bumps in the roads, whether they're large or small, cause your car's wheels to move abruptly upwards. If your car had totally rigid wheels mounted to an equally rigid frame, that jolt would make the ride extremely rough and uncomfortable. Just as bad, the tires lose a little (or a lot) of grip on the road surface, making safe, predictable handling a dicey proposition.

Your car as a whole is built to absorb and disperse shocks. But the suspension system itself has some important parts you can't do without. All cars have some sort of springs that help dissipate impacts. But those springs must work with shock absorbers, which slowly release the energy that springs absorb, preventing a bouncy, painful and unsafe ride.

You can see all of the details in our article called How Car Suspensions Work, or keep reading to find out about our next vital car system.

In terms of car tech, they're where the rubber (or rubber compound) really meets the road. It's your tires, and without them, an otherwise perfectly functional car isn't going anywhere fast.

Tires aren't just round doughnuts made of rubber. Like all car components, each part of the tire has evolved in a way that makes them superior to older versions. Engineers speak of tires by their specific sections, including tread, sidewall, belt, inner liner, bead assembly and more.

Even the rubber is anything but simple. Each type of tire contains a rubber compound, that is, stretchy, flexible rubber matched to various fillers that alter the tire's characteristics. Some tires are made to provide their best traction on dry surfaces, while others do their best work in the rain. Certain tires are built to have ultra-long lives (and are often ultra-expensive), while inexpensive tires usually contain less durable materials.

Good tires provide a smooth ride. But ultimately, tires are mostly about traction. The better your tires grip the road, the more control you have over the car's handling and the safer you and your family will be.

Tires are definitely simpler than most other car parts. But there's still plenty to know. You can read all about tires in How Tires Work or push ahead to our last — and, in some ways, most important — car component.

A lot of average cars are capable of speeds in excess of 100 miles per hour (160.9 kilometers per hour). That kind of velocity is really handy if you're outrunning an erupting volcano, but the simple act of safely stopping the car — from any speed — is a much more routine and important function. Brakes, then, are your best friend.

Cars have either disc brakes or drum brakes. When you depress the brake pedal, you're engaging a hydraulic system that ultimately presses brake pads (in disc brakes) or the shoes (in drum brakes) against the rotor or drum to slow it or stop it from turning completely.

Because their job involves so much friction, brake pads slowly wear out over time and must be replaced. When you don't keep up with this maintenance, you'll have a harder and harder time stopping the car precisely and safely.

Many late model cars have anti-lock brakes. Before the advent of these brakes, slamming on the brake pedal could potentially send the car into an uncontrollable skid. Anti-lock brakes pump the brakes rapidly to maximize braking force while preventing skidding and allowing the driver to steer out of danger.

As with all of the other car systems you've just learned about, you can read more in-depth information inHow Brakes Work.

So, now you know more about some of the parts that are fundamental to your car's performance. Without these systems and components, your car won't get very far — and neither will you.