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Ohm’s law

Fundamentals · Beginner · about 10 minutes · part of Zen’s Electronics Design Mastery

Voltage pushes, resistance resists, and current is the result: I = V / R. Double the voltage across a resistor and the current doubles. The ratio V / I stays fixed at R, so its V–I graph is a straight line.

Ohm’s law: the circuit on the simulator's bench

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How it works

I = V / R = 6 V / 1 kΩ = 6 mA

Rearranged: R = V / I and V = I · R. Cover the one you want in the triangle V over I × R.

00 A35 mA610 mA915 mA1220 mAVoltage across R (V)Current

Orange line: theory. Green dots: what you have measured so far.

Slope of the line = 1 / R = 1 mS (siemens).

Try it on the bench

  1. Select the supply and set 2, 4, 6, 8, 10 and 12 V. Each one adds a green dot, and they all land on the line.
  2. Change R to 470 Ω: the line gets steeper because the same voltage now pushes more current.
  3. Every meter reading obeys V = I · R. Check it with a calculator.
  4. Switch on Tools… → Operating-point overlay: every node voltage and every wire current appears on the mat at once.

Parts on the bench

In the course

Zen’s Electronics Design Mastery, module “DC Fundamentals”.

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