Video: Determining the Amount of Electrical Charge Delivered Using the Current Flow and the Time of the Current Flow

Which of the following electrical currents would deliver the greatest charge? [A] 0.25 A for 15 s [B] 0.05 A for 60 s [C] 0.10 A for 35 s [D] 1.0 A for 1.0 s [E] 20 A for 0.15 s

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Video Transcript

Which of the following electrical currents would deliver the greatest charge? A) 0.25 amps for 15 seconds. B) 0.05 amps for 60 seconds. C) 0.10 amps for 35 seconds. D) 1.0 amps for 1.0 seconds. Or E) 20 amps for 0.15 seconds.

Let’s have a quick recap of electrical currents. Imagine a metal wire. A metal wire is naturally filled with delocalized electrons. When an electrical field is applied, these electrons will move. Each electron carries a very small charge, about 1.6 times 10 to the minus 19 coulombs. This means it takes about 6.2 times 10 to the 18 electrons to make one coulomb.

If we have this many electrons passing a point in a wire in one second, we have a current of one amp. So, amps, with symbol A, are the same as coulombs per second. This gives rise to the formula 𝑄 equals 𝐼 times 𝑑, where 𝑄 is the charge in coulombs, 𝐼 is the current in amps, and 𝑑 is the time the current passes in seconds.

So, the currents in each option can be considered a rate of charge flow. So, all we need to do is take each electrical current, calculate the total amount of charge delivered, and find the greatest amount of charge delivered.

0.25 amps for 15 seconds delivers the total charge of 3.75 coulombs. 0.05 amps for 60 seconds delivers three coulombs. 0.1 amps for 35 seconds delivers 3.5 coulombs. 1.0 amps for 1.0 seconds delivers one coulomb. And finally, 20 amps for 0.15 seconds delivers three coulombs. Of these five options, the one that delivers the greatest charge, 3.75 coulombs, is 0.25 amps for 15 seconds.

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