Volts, amps and ohms, the simple way
Think water in a hose. Volts are the pressure. Amps are how much is flowing. Ohms are anything squeezing the hose.
The short version
- More resistance = less flow. A corroded connection is a kinked hose.
- 12V loads pull a lot more amps than the same thing on 120V. That's why 12V wiring is so thick.
- A part that's open (infinite ohms) gets full voltage across it but nothing flows. A short (near 0 ohms) pops the fuse.
Shop tip
You don't need the math to diagnose. You need to know a bad connection steals voltage when current flows.
Try it on a service call
Put the lesson to work on a hands-on troubleshooting case.
Keep going on 12V and batteries
Learn it
- Voltage drop: the test that finds bad grounds
- Practice: find the bad connection
- Batteries: lead-acid vs lithium
- Fuses, breakers and grounds
- Converter / charger
Prove it
- Back lights are dim
- Battery dies even on shore power
- Lithium won't charge on cold mornings
- Coach is dead, battery is fine
- Batteries dead after storage