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SCIENCE · INVESTIGATE AND EXPLAIN

Separate a physical time constant from a displayed one

The time coordinate itself can require calibration. Suppose displayed time s equals g times physical time t, with exact zero but unknown positive gain g. A zero-offset voltage 4e^(−t/τ) becomes 4e^[−s/(gτ)] on the displayed axis. The product gτ, not either factor separately, controls every point on that graph.

Learning outcome: Find two generator pairs with the same product gτ and compare their entire displayed curves. Then apply the independent calibration interval and state whether its premise covers each selected gain. Keep response validation distinct from clock validation.

Starting recap

Review charge continuity, definite integrals, first-order differential equations, initial conditions and signed source work. Distinguish displayed time from physical time.

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Try

For physical τ=1 s and clock gain 1.1, the displayed time constant is 1.1 display s. A second pair τ=1.1 s and g=1 gives the identical displayed curve. Applying the proposed narrow calibration would give approximately 1.078431 to 1.122449 s, which excludes the first true τ because its gain violates the premise.

Open the experiment

Predict

What does the displayed voltage response identify without independent clock evidence?

Experiment

Find two generator pairs with the same product gτ and compare their entire displayed curves. Then apply the independent calibration interval and state whether its premise covers each selected gain. Keep response validation distinct from clock validation.

Separate a displayed timescale from a physical one

Worked teaching model · synthetic values · Display time s=g t, with exact zero and positive clock gain g. Zero-offset voltage is 4 exp(−t/tau). Two records at displayed times 0 and 1 s fit only g tau. A fresh displayed-time record at 2 s tests that shape but cannot identify g separately. A distinct proposed clock calibration g in [0.98,1.02] is conditional, not asserted true for every slider setting.

Reset keeps your prediction, captures and practice history.

A clock-scaled response family

voltage (V)displayed time (display s)0340

Unlike graph quantities rescale independently; read units and values, not screen angles. 1: fit identifies only g times tau (solid). Joined curves show the supplied model, not additional observations.

Equivalent numerical coordinates for A clock-scaled response family

fit identifies only g times tau

displayed time (display s)voltage (V)
04
0.03753.865935
0.0753.736362
0.11253.611133
0.153.490101
0.18753.373126
0.2253.260071
0.26253.150805
0.33.045202
0.33752.943137
0.3752.844494
0.41252.749157
0.452.657015
0.48752.567962
0.5252.481893
0.56252.398709
0.62.318313
0.63752.240612
0.6752.165515
0.71252.092934
0.752.022787
0.78751.95499
0.8251.889466
0.86251.826138
0.91.764933
0.93751.705779
0.9751.648607
1.01251.593352
1.051.539948
1.08751.488335
1.1251.438451
1.16251.39024
1.21.343644
1.23751.29861
1.2751.255085
1.31251.213019
1.351.172363
1.38751.13307
1.4251.095094
1.46251.05839
1.51.022917
1.53750.9886322
1.5750.9554968
1.61250.9234721
1.650.8925206
1.68750.8626066
1.7250.8336952
1.76250.8057527
1.80.7787468
1.83750.7526461
1.8750.7274201
1.91250.7030396
1.950.6794763
1.98750.6567027
2.0250.6346924
2.06250.6134199
2.10.5928603
2.13750.5729897
2.1750.5537852
2.21250.5352243
2.250.5172856
2.28750.499948
2.3250.4831916
2.36250.4669968
2.40.4513447
2.43750.4362173
2.4750.4215969
2.51250.4074665
2.550.3938097
2.58750.3806106
2.6250.367854
2.66250.3555248
2.70.3436089
2.73750.3320924
2.7750.3209619
2.81250.3102044
2.850.2998075
2.88750.289759
2.9250.2800474
2.96250.2706612
30.2615896

At most 82 representative computed coordinates including endpoints; the plotted curve can use a finer grid. A table of a revealed generator is not independent measurement evidence.

Calculated quantities under the declared measurement model
QuantityValueUnit
Reading at displayed one second1.611561V
Fitted displayed time constant1.1display s
Fresh displayed two-second prediction0.6492824V
Fresh displayed two-second observation0.6492824V
Conditional physical time lower endpoint1.078431s
Conditional physical time upper endpoint1.122449s
Generator physical time constant1s
Generator clock gain1.1ratio

A fresh voltage sample tests the displayed response without independently calibrating the clock.

Because displayed s=g t, the response is 4 exp[−s/(g tau)]. Every positive pair with the same product g tau gives the same voltage versus displayed time. Only an independent clock constraint can bound physical tau. The proposed calibration [0.98,1.02] gives fit/1.02 through fit/0.98; if the selected generator gain lies outside that interval, the premise is false and the interval need not contain the true tau.

Predict before inspecting the values. Save contrasting records with assumptions and one alternative explanation. This virtual display does not certify practical measurement technique.

A fresh voltage sample tests the displayed response without independently calibrating the clock.

Because displayed s=g t, the response is 4 exp[−s/(g tau)]. Every positive pair with the same product g tau gives the same voltage versus displayed time. Only an independent clock constraint can bound physical tau. The proposed calibration [0.98,1.02] gives fit/1.02 through fit/0.98; if the selected generator gain lies outside that interval, the premise is false and the interval need not contain the true tau.

Captures preserve recipes and replay their calculated results. They are synthetic model evidence, not physical measurements.

Understand

State the current, source and measurement model

The time coordinate itself can require calibration. Suppose displayed time s equals g times physical time t, with exact zero but unknown positive gain g. A zero-offset voltage 4e^(−t/τ) becomes 4e^[−s/(gτ)] on the displayed axis. The product gτ, not either factor separately, controls every point on that graph.

Derive the integral or initial-value solution

From exact displayed readings at 0 and 1 s, fit T=−1/ln[y(1)/4]. A fresh displayed reading at 2 s tests the exponential response with that fitted T. It does not distinguish two pairs of g and τ that share the same product, even if many voltage records agree. An independent clock comparison supplies a different kind of evidence.

Test conservation, uncertainty and limits

If independent evidence justifies g in [0.98,1.02], physical τ lies between T/1.02 and T/0.98. This is a conditional interval. The slider intentionally permits gains outside that calibration range, so the interval is not guaranteed to cover every hidden generator state. A good voltage fit cannot repair a false clock-calibration premise.

Worked original case

For physical τ=1 s and clock gain 1.1, the displayed time constant is 1.1 display s. A second pair τ=1.1 s and g=1 gives the identical displayed curve. Applying the proposed narrow calibration would give approximately 1.078431 to 1.122449 s, which excludes the first true τ because its gain violates the premise.

Investigation

Find two generator pairs with the same product gτ and compare their entire displayed curves. Then apply the independent calibration interval and state whether its premise covers each selected gain. Keep response validation distinct from clock validation.

Changed-case practice

Try the changed case before feedback

If fitted displayed T=2 s and independently g is between 0.9 and 1.1, find the lower bound on physical τ in seconds.

This practice is public and unsaved. A matching number does not verify understanding. Retain your explanation, assumptions and changed-case evidence in the separate course workspace.

Sources and boundaries

Original derivations and synthetic evidence checked 31 October 2026 against the primary explanation. No live circuit construction, energized switching, component rating or electrical handling instruction is requested. Preserve first predictions, critique, revision and fresh assigned work separately from public practice. Software agreement does not certify measurement technique or learning.

Apply

What does the displayed voltage response identify without independent clock evidence?

Public practice checks a specific claim. It does not establish independent mastery.

Which initial state, calibration or constitutive assumption is needed for this conclusion, and what fresh evidence could test it?

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