Wi-Fi Card

Your phone has no network socket, and it is on the network all day. Somewhere inside it is a network card that talks by radio instead of by cable. In a computer, that part is called a Wi-Fi card.

1What a Wi-Fi card is

Wi-Fi card

A Wi-Fi card is a network card that connects a computer to a wireless network. It sends and receives data as radio waves through an antenna, instead of as signals down a cable. It is also called a wireless network adapter.

It does the same job as the Ethernet card from two lessons ago — turning the computer’s data into signals and back — and it has a MAC address of its own, just like an Ethernet card. Only the way the signal travels is different. The radio waves go to a Wi-Fi router or an access point, a box that is itself cabled into the network.

Which device has the Wi-Fi card?

The Wi-Fi card goes in the device that joins the wireless network — the computer, laptop or phone. It is not a part you add to the Wi-Fi router: the router already has its own radio built in. In the lab, the arrow shows the card going into the computer.

Joining by radio

Move the computer. Send a message each time. Then switch to wired and try again.

Wireless: the Wi-Fi card is inside the computer (the arrow shows where). It sends and receives radio waves to and from the router. Next to the router the signal is strong.

4 / 4

signal bars

yes

free to move?

The bars are a simplified picture: real signal strength depends on the router, the walls and what else is nearby.

2Three forms it comes in

🧩 A card inside

Fits a slot in a desktop computer, like an Ethernet card. Its antennas stick out of the back of the case.

🔌 A USB adapter

A small stick that plugs into a USB port. The easy way to add Wi-Fi to a computer that does not have it.

📱 Built in

Laptops, phones and tablets have the Wi-Fi chip and antenna built inside them. You never see it.

3Wi-Fi card or Ethernet card?

	Ethernet card	Wi-Fi card
Connects by	A cable with an RJ45 plug	Radio waves through an antenna
Talks to	A switch, hub or router, by cable	A Wi-Fi router or access point
Moving around	Tied to the cable	Free to move within range
Distance	As far as the cable reaches	Weakens with distance and walls
Speed and reliability	Usually faster and steadier	Can slow down when the signal is weak
Has a MAC address?	Yes	Yes

Why the school lab still uses cables

Forty computers that never move gain nothing from Wi-Fi, and a cable gives each one a steady, fast connection. Wi-Fi earns its place where people move about with laptops and phones.

4Check yourself

Quick Check

How does a Wi-Fi card send data?

Quick Check

A computer is moved into the next room, behind a thick wall, and its Wi-Fi becomes slow. Why?

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🔌 RJ45 Connector

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