Level 2 · Lesson 2.4

Electricity you need to know

Jimmy Bob, a friendly cartoon mountain man in a trucker cap and overalls

“Ohm's law is the one bit of arithmetic every ham carries in his back pocket.”

You'll be able to

apply Ohm's law and the power formula.

(E, volts) is electrical pressure, (I, amperes) is the flow, and (R, ohms) opposes the flow. says E = I × R. in watts is P = E × I. A radio drawing 10 amps from a 13.8-volt supply uses 138 watts.

Tap an underlined word for its meaning.

Try it

Ohm's law calculator

Fill in any two; leave one blank.

E (volts)I (amps)R (ohms)

E 13.8 VI 10 AR 1.38 ΩP 138 W

Quick check

Get 2 of 3 right to complete the lesson.

1. Ohm's law is…
2. A radio draws 10 amps from 13.8 volts. How much power?
3. Current is measured in…

Words from this lesson

WattPower supply