Kirchhoff's Current Law at a Series Junction (I₁ = I₂)

A fixed two-resistor series branch carries one unknown loop current. Record noisy ammeter readings I₁ and I₂ for several supply voltages; a linear fit of I₂ versus I₁ should recover unit slope — KCL at the intermediate node.

School· 24 min·Related simulator: Electricity & MagnetismKirchhoff's Laws (KCL & KVL)

Goal

Verify that in a series branch the current entering the junction equals the current leaving it (KCL): expect I₁ = I₂ within measurement error, i.e. slope ≈ 1 for I₂ plotted against I₁.

Equipment

Ideal DC voltage source
Fixed resistors R₁ = 220 Ω, R₂ = 330 Ω
Two ammeters in series (simulated)
Common ground

Theory

In steady-state DC, Kirchhoff's current law (KCL) states that the algebraic sum of currents into any node is zero. For a simple series connection of two resistors between two nodes, the single loop current is the same everywhere along the branch, so the readings on two ammeters wired in series must agree (up to instrument error).

Procedure

The bench uses a fixed series pair R₁ = 220 Ω and R₂ = 330 Ω between the ideal supply and ground (topology matches the “series only” mode of the related simulator).
Set the supply voltage V with the slider (try several values between about 5 V and 22 V).
Press “Record measurement” to log (V, I₁, I₂) with small independent ammeter noise.
Repeat for at least 6 different voltages spread across the range.
Inspect the linear fit of I₂ versus I₁: the slope should be close to 1 (KCL); the intercept should be close to 0.
Compare the fitted slope with the ideal 1 and write the conclusion.

Experiment

Fixed series R₁–R₂: two noisy ammeters should read the same loop current (KCL at N₂).

R₁ = 220 Ω and R₂ = 330 Ω are fixed on this bench (same as the “series only” case in the full simulator).

Supply voltage VV = 10.00 V

Ideal loop current: I = V/(R₁+R₂) ≈ 0.01818 A

Take ≥6 pairs (V, I₁, I₂) over a wide voltage range. The fit plots I₂ on the vertical axis versus I₁; the slope should be 1 if both meters see the same series current.

Measurements

№	Supply voltage V V	Current I₁ A	Current I₂ A
No measurements yet — take your first reading.

Data processing

Add at least 2 measurements to compute the fit.

Lab report

Opens the system print dialog — choose “Save as PDF” or your printer. Header and footer are hidden when printing.

One click opens the print dialog — choose “Save as PDF”.

Kirchhoff's Current Law at a Series Junction (I₁ = I₂)

Generated: 28 May 2026, 02:03

Goal

Verify that in a series branch the current entering the junction equals the current leaving it (KCL): expect I₁ = I₂ within measurement error, i.e. slope ≈ 1 for I₂ plotted against I₁.

Measurement table

#	Supply voltage V (V)	Current I₁ (A)	Current I₂ (A)
No measurements yet — take your first reading.

Fit and derived value

Add at least 2 measurements to compute the fit.

Conclusion

The fitted slope agrees with unity within tolerance, supporting KCL for this series junction. Residual mismatch comes from independent ammeter noise and a finite number of voltage points.

PhysSandbox virtual lab — values come from your session; add your own discussion of error sources.

Conclusion

The fitted slope agrees with unity within tolerance, supporting KCL for this series junction. Residual mismatch comes from independent ammeter noise and a finite number of voltage points.