If the values of "C1" and "R1" shown in the illustration were 1 microfarad and 100 k ohms, which of the listed time intervals would equal one 'time constant'? See illustration EL-0086.
• RC time constant in a resistor-capacitor circuit (τ = R × C) • Converting kilo-ohms and microfarads into base units of ohms and farads before multiplying • Using the graph in part B to relate one time constant to the charge/discharge curve of the capacitor
• How do you convert 100 kΩ into ohms, and 1 µF into farads? Once converted, what does multiplying those two numbers give you? • After you find τ in seconds, which answer choice is numerically closest to that value? • On the graph, at t = 1 time constant, about what percentage of full voltage has the capacitor reached on charge? Does that help you confirm that your calculated τ makes sense physically?
• Be sure you changed kΩ to Ω correctly (multiply by 1,000). • Be sure you changed µF to F correctly (multiply by 10⁻⁶). • After calculating τ = R × C, double-check that your final units are in seconds before comparing to the choices.
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