A student is modelling the discharge of a capacitor through a resistor. They use an oscilloscope to record the potential difference V V\,V across the capacitor and decide to model the decay numerically using a spreadsheet and the following approximation:
ΔVΔt=−0.50V \frac{\Delta V}{\Delta t} = -0.50 V ΔtΔV=−0.50VThe student chooses a constant time step of Δt=0.40 s\Delta t = 0.40\text{ s}Δt=0.40 s. The initial potential difference across the capacitor is 25.0 V.
Part of the student's modelling spreadsheet is shown below:
| t / st \text{ / s}t / s | Potential difference V V\,V at time t / Vt \text{ / V}t / V | Change in potential difference ΔV \Delta V\,ΔV in the next 0.40 s / V |
|---|---|---|
| 0.0 | 25.0 | -5.0 |
| 0.4 | 20.0 | |
| 0.8 | ||
| 1.2 |
What is the modelled value of V V\,V at t=1.2 st = 1.2\text{ s}t=1.2 s?
13.7 V13.7\text{ V}13.7 V
12.8 V12.8\text{ V}12.8 V
16.0 V16.0\text{ V}16.0 V
3.1 V3.1\text{ V}3.1 V
