WEBVTT
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The diagram shows an OR gate.
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If input A is one and input B is zero, what will the output be?
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Okay, so, in this question, we can see that we’ve been given an OR Gate.
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And we’ve been told that the value of input A is one and input B is zero.
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We have to use this information to work out what the output will be.
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So, to answer this question, let’s recall the truth table for an OR gate.
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And here is that truth table.
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Now an easy trick to memorise this truth table is to remember that an OR gate is called an OR gate because if either one of input A or input B is one, then automatically the output is going to be one as well.
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And we can actually see that in the truth table.
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When both input A and input B are zero, then the output is zero.
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But in every other combination of inputs, at least one of them is going to be one.
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So, in the second row, we can see that input B is one.
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In the third row, we can see that input A is one.
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And in the fourth row, we can see that both of them are one.
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And so, in these situations if either input A, or input B, or both are one, then the output is going to be one as well.
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And that’s why this is called an OR gate.
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So, that’s a good way to memorise the truth table.
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But let’s come back to the information we’ve been given in the question.
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We’ve been told that input A is one and input B is zero, and we need to work out what the output will be.
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So, to do this, we actually need to look at the third row in this table, where input A is one and input B is zero.
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And this row’s actually telling us that the output is one.
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And hence, we’ve found the answer to our question.
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For an OR gate, if input A is one and input B is zero, then the output will be one.