Voltage, Current, Resistance, and Ohm's Law

Contributors: CTaylor
Favorited Favorite 67

Ohm's Law

Combining the elements of voltage, current, and resistance, Ohm developed the formula:

alt text


  • V = Voltage in volts
  • I = Current in amps
  • R = Resistance in ohms

This is called Ohm’s law. Let’s say, for example, that we have a circuit with the potential of 1 volt, a current of 1 amp, and resistance of 1 ohm. Using Ohm’s Law we can say:

alt text

Let’s say this represents our tank with a wide hose. The amount of water in the tank is defined as 1 volt and the “narrowness” (resistance to flow) of the hose is defined as 1 ohm. Using Ohms Law, this gives us a flow (current) of 1 amp.

Using this analogy, let’s now look at the tank with the narrow hose. Because the hose is narrower, its resistance to flow is higher. Let’s define this resistance as 2 ohms. The amount of water in the tank is the same as the other tank, so, using Ohm’s Law, our equation for the tank with the narrow hose is

alt text

But what is the current? Because the resistance is greater, and the voltage is the same, this gives us a current value of 0.5 amps:

alt text

Tanks with their equivalent electrical meanings.

So, the current is lower in the tank with higher resistance. Now we can see that if we know two of the values for Ohm’s law, we can solve for the third. Let’s demonstrate this with an experiment.