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Chapter 18 · Electrical Quantities — Lesson 18.3
Ohm's Law: Voltage, Current & Resistance
Adjust the voltage and resistance in a simple circuit and watch current flow live through it, with an ammeter and voltmeter shown in their proper places. See how the V-I graph's gradient reveals the resistance.
Live Circuit & GraphI = 1.50 A
6.0 V
4 Ω
Readouts
Voltage V
6.0 V
Current I
1.50 A
Resistance R
4 Ω
For a fixed resistor, the V-I graph is a straight line through the origin — that’s Ohm’s law. The line’s gradient is the resistance: a steeper line means a bigger R.
V = I R
voltage = current × resistance
What Each Variable Means
V
Voltage (p.d.)
The push driving current through the circuit, in volts (V).
I
Current
The rate of flow of charge, in amps (A) — shown by the moving dots.
R
Resistance
R = V/I, in ohms (Ω). A bigger R means less current for the same voltage.