<^< Examples: Kirchoff's Current Law | Course Index | Kirchoff's Voltage Law >^>
| Objective:
| To investigate Kirchhoff's Current Law.
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| Underpinning knowledge:
| Voltage, current and resistance. Ohm's Law. Kirchhoff's Current Law.
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| Apparatus:
| TINA circuit file, or apparatus to make the following circuit.
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| TINA Circuit File:
| Click here to download circuit file
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| Initial Settings:
| 8V and 12V batteries. R1 = 1kΩ, R2 = 2kΩ, R3 = 3kΩ.
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| Requires:
| Paper, Linear graph paper, pen or pencil.
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| Instructions:
(a) Using initial settings verify that I1 - I2 + I3 = 0 (or, more conveniently, that I1 + I3 = I2).
(b) Change R1 to 3kΩ, R2 to 1kΩ and R3 to 2kΩ. Confirm, once again that I1 - I2 + I3 = 0.
(c) Finally, make R1 to 2kΩ, R2 to 3kΩ and R3 to 1kΩ. Once again, confirm that I1 - I2 + I3 = 0.
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Observations:
(a) Is Kirchhoff's Current Law obeyed?
(b) The convention adopted in the formula, I1 - I2 + I3 = 0, is that current flowing towards the junction is positive whilst current flowing away is negative. How is it possible to determine the direction of current in the circuit?
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| Further work:
Add a further battery of 10V and a fourth resistor of 4kΩ in series with an ammeter connected to the junction in the circuit. Derive the Kirchhoff's Current Law equation for this new circuit (you will have to consider four currents in the circuit; I1, I2, I3 and I4) and confirm that the Current Law is obeyed by inserting measured values into the equation
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<^< Examples: Kirchoff's Current Law | Course index | Kirchoff's Voltage Law >^>
