A capacitor is a fascinating electrical component. It consists of two metallic conductors separated by an insulator. A capacitor can store charge and energy. Mobile phones and cameras use capacitors to provide a powerful flash of light. But did you know that a capacitor can be used to demonstrate the mathematics of exponential functions?
Connect the terminals of a charged capacitor across a resistor. The potential difference across the capacitor decreases in a very clear, predictable manner known as exponential decay. The rate of decay depends on the resistance and the capacitance of the circuit. You can therefore use a capacitor-resistor circuit as an electronic timer. For example, your battery-operated wristwatch is likely to contain miniaturised capacitors and resistors.
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