Today’s Wonder of the Day was inspired by Youssef from Morton Grove, IL. Youssef Wonders, “How do keycards unlock a door” Thanks for WONDERing with us, Youssef!

Have you ever stayed in a hotel? Many kids enjoy visiting hotels on family vacations or school trips. And what’s not to love? They have comfy beds, large swimming pools, and free breakfast. Plus, you get to swipe your way into the room with one of those cool key cards!

Besides hotels, you’ve likely seen key cards used in many places. As a modern alternative to metal keys, they’re common in banks, hospitals, and anywhere else security is important. Have you ever stopped to WONDER how key cards work?

The answer to that question depends on just what type of key card you’re talking about. Yes, there is more than one! For several years, most key cards used a magnetic stripe. But today, cards that use radio frequency identification (RFID) and near field communication (NFC) are becoming more common.

Think back to the last time you saw a key card. Did it have a black stripe on the back like a debit card? That was a magnetic stripe, also called a magstripe. It’s made up of many small magnets, each with its own north and south pole. 

Before you use a key card with a magstripe, it has to be “written.” That means someone uses an encoder to magnetize the stripe. The key card can then be swiped in a card reader. This reads the magnetic field and unlocks the door if the card has the right authorization

What about an RFID key card? These contain a chip and a small antenna. The chip contains security information, which can be communicated to a card reader by the antenna through radio waves. In contrast to magstripe cards that need to be swiped through a card reader, RFID cards just need to be held close to the reader.

NFC key cards work in a similar way. The main difference is they can be programmed for two-way communication. RFID cards use one-way communication. That means information only flows from the key card to the reader. With NFC, however, data can flow both ways. NFC is the same technology that enables people to use their smartphones as digital wallets. 

When was the last time you used a key card? As a kid, you may not need them often. However, many adults use them to get into secure locations at work. When you start your career, you may also find yourself using a key card every day.

Of course, it’s also possible you’ll never use a key card as an adult. By then, people may be using a completely different type of key. That’s part of the nature of technology—it changes quickly! How do you think key cards might change in the future? What new inventions might even replace them?


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