The Language of Measurement
Ratio, Proportion & Percentage
12 min · 2 worked examples · 3 questionsFree
Voltage dividers, component tolerance and efficiency, all the same underlying idea.
After this lesson you can
- Say whether two quantities are directly or inversely proportional
- Work out a voltage divider without a calculator
- Turn a tolerance or an efficiency into a real number
Direct and inverse proportion
Two quantities are directly proportional if doubling one doubles the other. In Ohm's law, with resistance fixed, current is directly proportional to voltage: double the voltage, double the current. We write I ∝ V.
They are inversely proportional if doubling one halves the other. With voltage fixed, current is inversely proportional to resistance: double the resistance, halve the current. We write I ∝ 1/R.
Recognising which relationship you are dealing with lets you predict behaviour without calculating anything, a genuinely useful engineering instinct.
In the full lesson
- Direct and inverse proportion
- The voltage divider
- Percentages and tolerance
- Efficiency
Free with an account. Read it, work the examples, answer the questions, then build it in the simulator.