Beginner Fundamentals

Ohm's Law

Explore V = IR. Adjust voltage or resistance and watch current change in real time.

// Ohm's Law

Simulator: Falstad CircuitJS1 (GPL-2.0) — hosted by falstad.com

This circuit has a 9 V source and a 1 kΩ resistor forming a simple loop. The simulator shows current flowing through the resistor.

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Current direction follows conventional flow: out of the positive terminal, through the circuit, back to the negative terminal.
Apply Ohm's Law: I = V / R. With V = 9 V and R = 1 kΩ, calculate the expected current.

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I = 9 / 1000 = 0.009 A = 9 mA
In the Falstad simulator above, right-click the resistor and set its value to 4.5 kΩ. Observe how the current changes.

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I = 9 V / 4500 Ω = 2 mA. Doubling resistance halves the current.
Try different values. Notice that current and resistance are inversely proportional when voltage is fixed.

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This is the essence of Ohm's Law: V = IR is always satisfied in a linear resistive circuit.

Expected values

Probe	Value	Unit
V	9	V
I	0.009	A