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Complete Electronics Self-Teaching Guide with Projects by Harry Kybett, Earl Boyson

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Ohm's Law

4 Ohm's law states the fundamental relationship between voltage, current, and resistance.

Question

What is the algebraic formula for Ohm's law? _____

Answer
equation

This is the most basic equation in electricity, and you should know it well. Some electronics books state Ohm's law as E = IR. E and V are both symbols for voltage. This book uses V to indicate voltage. When V is used after a number in equations and circuit diagrams, it represents volts, the unit of measurement of voltage. Also, in this formula, resistance is the opposition to current flow. Larger resistance results in smaller current for any given voltage.

5 Use Ohm's law to find the answers in this problem.

Questions

What is the voltage for each combination of resistance and current values?

A. R = 20 ohms, I = 0.5 amperes

V = _____

B. R = 560 ohms, I = 0.02 amperes

V = _____

C. R = 1,000 ohms, I = 0.01 amperes

V = _____

D. R = 20 ohms I = 1.5 amperes

V = _____

Answers
A. 10 volts
B. 11.2 volts
C. 10 volts
D. 30 volts

6 You can rearrange Ohm's law to calculate current values.

Questions

What is the current for each combination of voltage and resistance values?

A. V = 1 volt, R = 2 ohms

I = _____

B. V = 2 volts, R = 10 ohms

I = _____

C. V = 10 volts, R = 3 ohms

I = _____

D. V = 120 volts, R = 100 ohms

I = _____

Answers
A. 0.5 amperes
B. 0.2 amperes
C. 3.3 amperes

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