# Resistivity In Wire

*Register to read the introduction…*The units associated with resistivity are thus ohm.m (ohm -

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This is resistance, which is measured in units called ohms. Resistance is a term that describes the forces that oppose the flow of electron current in a conductor. All materials naturally contain some resistance to the flow of electron current. We have not found a way to make conductors that do not have some resistance.

If we use our water analogy to help picture resistance, think of a hose that is partially plugged with sand. The sand will slow the flow of water in the hose. We can say that the plugged hose has more resistance to water flow than does an unplugged hose. If we want to get more water out of the hose, we would need to turn up the water pressure at the hydrant. The same is true with electricity. Materials with low resistance let electricity flow easily. Materials with higher resistance require more voltage (EMF) to make the electricity flow.

The scientific definition of one ohm is the amount of electrical resistance that exists in an electrical circuit when one amp of current is flowing with one volt being applied to the

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V = I x R

R = V/I

*All of these variations of Ohm's Law are mathematically equal to one another.

Let's look at what Ohm's Law tells us. In the first version of the formula, I = V/R, Ohm's Law tells us that the electrical current flowing in a circuit is directly proportional to the voltage and inversely proportional to the resistance. In other words, an increase in the voltage will tend to increase the current while an increase in resistance will tend to decrease the current.

The second version of the formula tells us that if either the current or the resistance is increased in the circuit, the voltage will also have to increase. The third version of the formula tells us that an increase in voltage will result in an increase in resistance but that an increase in current will result in a decrease in resistance.

As you can see, voltage, current, and resistance are mathematically, as well as, physically related to each other. We cannot deal with electricity without all three of these properties being