Question Video: Calculating the Potential Difference across a Cell Science

A cell does 20 joules of work to separate 4 coulombs of charge. What potential difference does this create across the terminals of the cell?

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Video Transcript

A cell does 20 joules of work to separate four coulombs of charge. What potential difference does this create across the terminals of the cell?

This question asks us to calculate a potential difference. The information we are given is how much work it took to separate an amount of charge. Given what we are looking for and what we have to work with, we can recall a formula that relates all three of these quantities. The formula we need tells us that the potential difference across the terminals of a cell is equal to the work done to separate the charge divided by the total amount of charge that was separated.

When we substitute 20 joules for the work and four coulombs for the charge, we have that the potential difference is 20 joules divided by four coulombs. Now, to figure out what value this is as a potential difference, we first divide 20 by four, which is five. And then we notice that the units in the numerator are joules and the units in the denominator are coulombs. Whenever we have a numerator with units of joules divided by a denominator with units of coulombs, the units of the final quantity are volts. So the potential difference that we are looking for is five volts.

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