Question Video: Comparing the Electrical Resistances of Wires with Different Lengths Science

Any wire will have some amount of electrical resistance. There are two unequal lengths of identical wire. Which one of the following sentences is correct? [A] Both wires have the same resistance. [B] The wire of greater length has the greater resistance. [C] The wire of greater length has the lower resistance.

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Video Transcript

Any wire will have some amount of electrical resistance. There are two unequal lengths of identical wire. Which one of the following sentences is correct? (A) Both wires have the same resistance. (B) The wire of greater length has the greater resistance. (C) The wire of greater length has the lower resistance.

Okay, let’s say we have two bits of wire here. And in every way, these wires are the same. That is, they’re made of the same material, they had the same diameter, and so on. Except, as we can see, one wire is longer than the other. We want to compare the electrical resistances of these wires. Imagine we get two identical batteries, and we connect up one battery to each wire. This will cause electrical charge to flow to each wire and then through each one.

But here’s the thing. The wires resist the flow of charge. They make it harder for current to pass through the circuit. We can think of this resistance being caused by the material in the wire getting in the way of the moving charge. The more material there is in front of the moving charge, the harder it is for the charge to move forward. That means the charge passing through the shorter wire has to get through this amount of resistive material. But then, the charge passing through the longer stretch of wire has to get through this much material. The longer section of wire is harder for charge to pass through. That means it has a greater resistance. We choose answer option (B). The wire of greater length has the greater resistance.

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