20 lines
708 B
Markdown
20 lines
708 B
Markdown
---
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tags: [electricity, radio, ham-study]
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---
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Impedance is not the same thing as [resistance](./Resistance.md) although it is
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a related concept.
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Resistance is opposition to the flow of current **in both
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[AC and DC](./Voltage_sources.md)** circuits. It is a quantity that **remains
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constant**. Resistance in a circuit causes electrical energy to be dissipated as
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heat.
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In contrast, impedance is not constant. It changes based on the frequency of the
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current and it only applies to AC circuits.
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Impedance is calculated as the resistance _plus_ the frequency-dependent
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opposition to alternating current from components such as capacitors and
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inductors.
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> Both resistance and impedance are measured in Ohms
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