Electronics Fundamentals to ESP32 / Electricity Fundamentals
Voltage, current and resistance - the three quantities
What pushes charge, how much flows, and what holds it back.
Video coming on Sketch To System TV - the embed will appear here once a video ID is added in admin.
By the end of this lesson you will be able to
- Explain voltage, current and resistance in plain words
- Give one everyday example of each
- Read a circuit diagram's supply voltage
Every circuit is about moving electric charge. Voltage (volts, V) is the push. Think water pressure in a pipe. Current (amps, A) is how much charge flows per second, like litres per second. Resistance (ohms, Ω) is what holds the flow back, like a narrow section of pipe.
A 9 V battery does not 'send 9 volts of electricity' into a circuit. It provides a 9 V push between its two terminals. What flows depends on what you connect across it.
Rule of thumb for beginners: voltage is chosen, current is what the circuit draws, resistance is what you design with.
Try it
With a multimeter, measure a AA battery: set it to DC volts, touch red to +, black to -. You should read about 1.5 V. Reverse the leads and note the minus sign.
Lesson completion is earned by passing the quiz below.