Varistor facts for kids
A varistor, also known as a VDR (which stands for voltage dependent resistor), is a special type of resistor. It changes how much electric current can flow through it based on the voltage (or electrical pressure) it experiences.
Think of a varistor like a smart gate for electricity. Most of the time, this gate is closed, meaning it has very high electrical resistance and lets almost no current pass. But if the voltage across it suddenly gets too high, like during a power surge, the gate quickly opens wide. This means its resistance drops a lot, letting the extra electricity flow through it safely, instead of damaging other parts of an electronic device.
Contents
How Varistors Protect Electronics
When the voltage across a varistor reaches a certain level, called the "threshold voltage," something amazing happens inside it. The electrical structure near its tiny internal boundaries changes, causing its resistance to drop super fast. It can go from millions of ohms (a unit of resistance) down to just a few hundred ohms in a flash!
Protecting Against Power Surges
The best thing about varistors is that they can handle a lot of extra energy, and they can reset themselves. Once the dangerous high voltage goes away, their resistance goes back to being high, and they are ready to protect again. This makes them perfect for surge protectors.
You can find varistors in many places because they can be made to work at different voltage levels and handle different amounts of energy. A great example of their power is in big electrical substations. Here, they are used to protect all the important equipment from powerful things like lightning strikes! They react very quickly, don't need much looking after, and don't wear out easily. This makes them almost perfect for keeping our power systems safe.
Why Varistors are Great for Protection
Varistors are used to protect all sorts of electronics from voltages that could harm their delicate parts. They act like a safety valve, diverting dangerous electricity away from sensitive circuits. This helps your electronics last longer and stay safe from unexpected power spikes.
Images for kids
-
Modern varistor schematic symbol.
-
Varistor current vs voltage for zinc oxide (ZnO) and silicon carbide (SiC) devices
-
High voltage varistor
-
Plug assembly with surge protector circuitry
-
Western Electric 3B varistor made in 1952 for use as click suppressor in telephone sets
-
Circuit of the traditional construction of varistors used as click suppressors in telephony
-
Western Electric Type 44A varistor manufactured in 1958, mounted on a U1 telephone receiver element for click suppression.
See also
In Spanish: Varistor para niños
