How Does a Car Work? A Kid-Friendly Guide

From energy to motion

A car is a machine that carries people and belongings from place to place. To move, it needs energy, a way to turn that energy into motion, and wheels that can push against the road. Most cars use either an internal-combustion engine, an electric motor, or both.

In a gasoline car, fuel stores chemical energy. The engine mixes fuel with air and burns it inside small chambers called cylinders. The hot gases push parts called pistons, and the pistons help turn a shaft. A series of parts then carries that turning force to the wheels. The engine does not simply spin the wheels directly; the transmission helps match the engine’s turning speed to the car’s needs.

An electric car gets energy from a large rechargeable battery. The battery sends electricity to a motor, where magnetic forces make parts turn. That turning motion reaches the wheels through the car’s drive system. Many electric cars do not need the same kind of multi-gear transmission found in many gasoline cars, though designs differ.

A hybrid car combines an engine and an electric motor. Depending on its design and driving conditions, it may use either power source or both. In all these types, the basic result is alike: energy makes the wheels turn, and the tires push backward on the road so the car moves forward.

How the main parts work together

Think of a car as a team of systems rather than one single machine. Each part has a job, and the parts must work together for the car to respond to the driver.

Power source: The engine or motor provides turning force.
Transmission and drivetrain: These parts carry power toward the wheels and help deliver it in a useful way. The drivetrain may send power to the front wheels, rear wheels, or all four, depending on the car.
Wheels and tires: Tires grip the road. Their contact with the road lets the car start, turn, and stop.
Steering: Turning the steering wheel changes the direction of the front wheels in many cars, guiding the vehicle along a curve.
Brakes: Brakes create friction to slow the wheels. In many cars, pressing the brake pedal makes brake pads squeeze rotating discs.

The accelerator pedal tells the car to provide more power; it does not work like a simple on-off switch in every vehicle. The brake pedal asks the braking system to slow the car. The steering wheel changes direction, but the tires need enough grip to follow that direction. If the road is slippery, that grip can be reduced.

What happens when you drive

When a driver starts a car, its systems check or prepare important equipment, then the engine or motor can provide power. The driver selects a driving mode or gear as the owner’s manual describes. Pressing the accelerator requests more power, and the drivetrain turns the wheels. The tires push against the road, moving the car.

To turn, the driver steers while the tires follow a curved path. To slow or stop, the driver presses the brake pedal. In a gasoline car, the engine may keep running while the car is stopped; the brakes hold the wheels still. In some cars, an automatic stop-start feature may temporarily turn off the engine at a stop and restart it when needed.

Many electric and hybrid cars also use regenerative braking. During some slowdowns, the motor works like a generator, converting some of the car’s motion into electrical energy that returns to the battery. It cannot capture all the energy, so regular friction brakes are still needed.

Why cars have so many supporting systems

A car needs more than power and wheels. A cooling system helps keep an engine from getting too hot. A lubrication system moves oil around engine parts to reduce friction and wear. The exhaust system carries gases away from a gasoline engine. Electric cars do not have an engine exhaust system, but they still have cooling, electrical, and control systems.

The battery in a gasoline car usually powers equipment such as lights and electronic controls, and helps start the engine. The much larger battery in an electric car stores the energy that runs its motor. Cars also have suspension parts, such as springs and shock absorbers, which help the tires stay in contact with uneven roads and make the ride less bumpy.

Dashboard displays and warning lights tell the driver about the car’s status. A warning light can mean that a system needs attention; its meaning varies, so drivers should check the owner’s manual rather than guess. Seat belts, airbags, lights, mirrors, and other safety features serve different purposes, and none makes careful driving unnecessary.

Gasoline, electric, and hybrid cars

Gasoline cars carry fuel in a tank and make power by burning it in an engine. Electric cars store electricity in a battery and use a motor. A hybrid has both an engine and a motor, along with systems that manage their power. These are different ways to supply energy, not different ways for tires to grip the road.

Electric cars are often quiet because electric motors make less engine noise than gasoline engines, but quiet does not mean they are not moving. Gasoline cars produce exhaust where the engine operates; electric cars do not produce exhaust from a tailpipe while driving, though the electricity used to charge them may come from different sources. Hybrid details vary by model, so the owner’s manual is the best place to learn how a particular car behaves.

How a car stays safer on the road

Safety depends on the car, the driver, road conditions, and other people nearby. Seat belts help hold occupants in place, while airbags are designed to work with seat belts in certain crashes. Brakes, tires, lights, mirrors, and steering all need to function properly. A car’s safety features cannot prevent every crash or replace attention and good judgment.

Children should ride in a seat or restraint that fits them and the vehicle, following its instructions and local law. A child should never play with the pedals, steering wheel, gear selector, or other controls. Drivers should follow the owner’s manual and local law, keep attention on driving, and arrange qualified service when a safety-related problem appears.

Frequently Asked Questions

How does a car move forward?

An engine or electric motor turns the wheels. The tires push backward against the road, and the road pushes the car forward.

Does the accelerator make a car go faster?

It asks the engine or motor for more power, which can make the car speed up. How quickly it responds depends on the vehicle and driving conditions.

Why do cars need gears?

Gears help the power source work effectively at different speeds and when starting or climbing. Many electric cars use a simpler drive arrangement, so not every car shifts through several gears in the same way.

Can an electric car drive without gasoline?

Yes. A fully electric car uses electricity stored in its battery rather than gasoline to power its motor. A hybrid still has an engine as well as an electric motor.

Why do cars need brakes if they can slow down on their own?

Letting off the accelerator may reduce power, and some vehicles can use regenerative braking, but neither replaces the friction brakes. Brakes are needed to control speed and bring the car to a stop.

Further reading: U.S. Department of Energy. Details can change, so check the official page for anything that matters to you. Spotted a mistake? Tell us. How we write an answer.