Time constant
What Time constant means in Physics A-Level, as defined for AQA, OCR.
Definitions of Time constant
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Reference: AQA
The product of resistance and capacitance, τ = RC, equal to the time for charge, potential difference or current to fall to 1/e of its initial value during discharge, about 37%.
The time constant τ of a capacitor–resistor circuit is defined by τ = CR, where C is capacitance in farads and R is resistance in ohms.
The product of resistance and capacitance, τ = RC, which has units of seconds because an ohm multiplied by a farad gives a second.
The value τ = RC, which determines the rate, with a larger resistance or capacitance giving a slower approach to the final value.
A quantity increased by raising either resistance or capacitance, lengthening each part of the cycle and lowering the frequency.
The quantity τ = CR, which determines the rate of charging and discharging in a capacitor–resistor circuit.
Topics that use Time constant
- Astables (A-level only) (AQA A-Level)
- Capacitor charge and discharge (A-level only) (AQA A-Level)
- Charging and discharging capacitors (OCR A-Level)
Related terms
- Capacitor charging and discharging
- Area under a graph
- Circuit setup for capacitor investigations
- Current, charge and voltage graphs
- Determining the time constant from a graph
- Differential equation for discharging a capacitor
- Discharging circuit
- Effect of larger R or C
Using Time constant in the exam
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