Voltage, Current, Resistance

Almost every circuit you will ever build comes down to three quantities working together:

• Voltage (V) — the push, measured in volts. Think of it as water pressure.
• Current (I) — the flow, measured in amps. Think of it as the flow rate of water.
• Resistance (R) — the restriction, measured in ohms (Ω). Think of a narrow pipe squeezing the flow.

The water tower analogy makes this click. A tall tank creates high pressure (voltage). Open the tap and water gushes out (current). Now pinch the hose with a narrow nozzle (resistance) and less water gets through, even though the tank pressure hasn’t changed. Electronics behaves exactly the same way.

These three are not independent — they are locked together. Raise the voltage (more pressure) and current climbs. Raise the resistance (a tighter pinch) and current falls. Master that single tug-of-war and the rest of electronics follows.