| In this article, part II of reading audio specifications, I will explain, how the amount of current I, in a circuit, depends on resistance R, and voltage V. If you know 2 of the factors, using Ohm's law, you can calculate the third factor. You will learn the formulas for Ohm's law, and apply them to find each one of these factors. The formula for current is I = V divided by R. If the resistance is kept constant in a circuit, and the voltage is varied, the current is varied in the same proportion. An example of this can be seen in a light bulb. If the light bulb has 10 volts applied to it, a meter will indicate the current at that voltage. As the voltage decreases, the current decreases and makes the light bulb dimmer. I is the amount of current through the resistance across the source of potential difference, or voltage. There has to be a resistance between the plus side, and minus side of a battery. Anyone who has touched both ends of jumper cables together proves this. It is called a direct short to ground in a circuit. Lets connect a 8 Ohm resistor across the plus & Minus side of a 12V battery. How much is the current I. I = 12V divided by R of 8 Ohm's = 1.5A or amps for I. Voltage is calculated by the formula V = I x R. If I equals 1.5A, and R = 3 Ohm's, the voltage will be 4.5V across the resistor. The formula for resistance is R = V divided by I. This is the third and final version of Ohm's law. Let's prove the relationship between these three factors of Ohm's law, In the last problem, voltage was equal to 4.5V. We also know that I = 1.5A, and R = 3 Ohm's. 4.5v divided by 1.5A, has a resistance of 3 Ohm's, proving this relationship.
In conclusion, now, you know how to calculate, I, R, and V in a circuit. We learned that by knowing two factors, the third can be calculated using Ohm's law. We also proved, there is a relationship between all three factors. In my next article, you will learn units of measurement for calculating, mega, kilo, milli, and micro. In addition, we will learn how to calculate power & power dissipation in resistance.
Problems for this article:
1. With 10V across an R of 5 Ohm's what is the current I?
2. When 10V produces 2.5A, R is equal to?
3. With 8A through a 2 ohm resistor, the I x R voltage is?
If you want to check your answers to these problems, check out the articles page on our website. Thank you & many blessings to you. Bradley Angell |
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