Resistors in parallel

When resistors are connected in parallel the current has more than one path that it can take, therefore a larger current will flow. Because of this is the total resistance is always going to be less than either of the individual resistors.

Showing that Resistors in parallel pass more current and therefore have a lower resistance in total
Resistors in parallel pass more current

In the photograph below two resistors are connected in parallel and have a current flowing through. The total current is being measured as is the potential difference across both the resistors. From these two values therefore, we can calculate the total resistance.

Showing how to measure the total resistance of two resistors in parallel
Two resistors in parallel

Using the equation that R the resistance equals potential difference divided by current we calculate the total resistance:

Calculation of total resistance

You can see that the total resistance is about half of each of the individual values which are nominally of 100 ohms but actually just slightly less than that (we have measured the value before). Using the equation for calculating the value of resistors in parallel, which is that the inverse of the total resistance is equal to the inverse of each of the individual resistances:

Using the equation for resistors in parallel
Resistors in parallel equation

Just to give you one more example. Suppose we have three resistors in parallel of 4, 6 and 12 ohms, we can use the equation to calculate the total resistance:

And you can see that the total resistance is very much less than any of the individual values

You might find it easier to watch the second part of the video below in which the same examples are used.