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MODULE V - FUNDAMENTALS OF ELECTRONICS OHMS LAW Ohm's Law states that, at constant temperature, the electric current flowing in a conducting material is directly proportional to the applied voltage, and inversely proportional to the resistance Ohms law, very obviously named after Mr. Ohm, defines the relationship between power, voltage, current and resistance. These are the very basic electrical units we work with. The principles apply to a.c., d.c. or r.f. (radio frequency). What are the ohms law formulas? To make it much easier for you I have put all the relevent formulas together for you here complete with worked examples of ohms law. You will notice the formulas share a common algebraic relationship with one another. For the worked examples voltage is E and we have assigned a value of 12V, Current is I and is 2 amperes while resistance is R of 6 ohms. Note that "*" means multiply by, while "/" means divide by.

For voltage [E = I * R]       E (volts) = I (current) * R (resistance)   OR   12 volts = 2 amperes * 6 ohms For current [I = E / R]       I (current) = E (volts) / R (resistance)   OR   2 amperes = 12 volts / 6 ohms For resistance [R = E / I]   R (resistance) = E (volts) / I (current)   OR   6 ohms = 12 volts / 2 amperes Notice how simple it is? Now let's calculate power using the same examples. For power        P = E2 / R   OR   Power = 24 watts = 122 volts / 6 ohms Also        P = I2 * R   OR   Power = 24 watts = 22 amperes * 6 ohms Also        P = E * I   OR   Power = 24 watts = 12 volts * 2 amperes That's all you need for ohms law - remember just two formulas: for voltage E = I * R and; for power P = E2 / R You can always determine the other formulas with elementary algebra. Ohms law is the very foundation stone of electronics! Knowing two quantities in ohms law will always reveal the third value. I suggest you print these formulas out and paste them onto scrap cardboard to keep your ohms law as a handy reference until you are quite familiar with it.

Electron Theory and Atoms Resistance Resistors Ohms Law Current and Voltage Voltage Dividers Capacitance Inductance Reactance Resonance and Impedance Diodes Transistors "Q" Radio Terminology A-L Radio Terminology M-Z Atttenuators Chokes Decibel & Toroids Digital Basics Power Supplies Conclusion  Subscribe For A Free Ham Radio E-Tutorials  Back To Top

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