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Electronics For Kids For Dummies. Shamieh Cathleen
Читать онлайн.Название Electronics For Kids For Dummies
Год выпуска 0
isbn 9781119215714
Автор произведения Shamieh Cathleen
Жанр Зарубежная образовательная литература
Издательство John Wiley & Sons Limited
Understanding resistance
Every resistor has a value known as its resistance (what a surprise). The higher the resistance, the more the resistor restricts current. Resistance is measured in ohms (pronounced “omes”), and the symbol for ohms is Ω (which looks like an upside-down horseshoe and is the Greek letter omega).
Some resistances are measured in kilohms (pronounced “kill omes”), which means thousands of ohms. The symbol for kilohms is kΩ. Other resistances are so large they are measured in megohms (pronounced “meg omes”), which means millions of ohms. The symbol for megohms is MΩ. (You may be familiar with the prefixes, kilo, which means thousands, and mega, which means millions, from your math classes. And you’ve probably heard of measurements such as kilometer, as in the k in a 5k race, and megabyte, as in “My laptop has 4 megabytes of RAM.”)
For your LED flashlight, you need a resistor with a value of 470 Ω. But resistors don’t have their values stamped on their cases, so you need to know how to identify a 470 Ω resistor. You can tell what the resistance of a specific resistor is by looking at the colored bands on its case. Think of the colored bands as a code. The color and position of the bands tell you the value of the resistance.
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