Quick recap and a break.
- Analog pins are basically voltmeters — they read voltage relative to GND.
- Our LDR test uses a closed circuit from 5V back to GND.
- To read after this LDR, we add a second “choke” between the measuring point and GND.
- The two resistors form a voltage divider.
Back to the syringe
Voltage is like water pressure.
Your hand pushes the plunger. Push harder on the same syringe and the pressure goes up.
Current is the flow rate.
It is the VOLUME of water
moving past a point
every second — like liters per second.
Liters per second sounds like “speed,” like km/h.
So, using a car analogy, voltage would be…?
The water analogy
If voltage is pressure — the push —
then current is flow rate — liters per second.
That is how much passes per second, rather than the speed of one drop.
The car analogy
If we use the car’s “speed” as a memory aid for current,
then the driving push — pressing the gas pedal — is a memory aid for voltage.
A loose analogy: electrical current counts charge per second; it is not the travel speed of an electron.
Let’s play! Make your own!
A light-level tester with three LEDs.
Choose what each light level should show. Give each LED its own series resistor.