Exam Questions - Logic Gates

Example Question 1

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2

Question 2 requires you to match logic gate symbols to their name by drawing a straight line to link them.

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Example Question 2

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10

(a) Question 10 (a) requires you to fill in the truth table for a NOR gate.  Remember that a NOR gate is essentially the opposite of an or gate. X will only be 1 if Neither of the inputs are 1 and both of them are not 1.

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(b) Question 10 (b) asks you to write a logic statement for the given diagram

For this question 1 mark would be awarded for each correct part of the answer.

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The whole answer should look something like this:

X = (A AND B) AND (C OR NOT B)

1 mark for each of the following sections

(A AND  B) = 1 mark
AND = 1 mark
​(C OR NOT B) = 1 mark

Example Question 3

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10

Below are the answers for the diagram and truth table that you are required to produce for question 10.  Remember that for 10(a) a mark is awarded for each correct gate with the correct inputs. This means that marks can be awarded even if the diagram is not perfect.
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Example Question 4

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5

(a) Question 5 (a) provides you with a logic statement and asks you to draw a diagram. Remember to take your time here to fully understand the statement.  1 mark is awarded for each correct gate.

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(b) Question 5 (b) asks for you to draw an XOR gate and then explain the function of it. When drawing gates remember to take your time and make sure that it is clear, you do not want the examiner to get confused by what gate you are trying to draw!

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Example Question 5

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7

Question 7 provides you with a logic statement and asks you to draw a diagram.  This is quite a long logic statement with three bracketed sections.  The question is worth 7 marks so you should make sure to spend some time planning this diagram.
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Example Question 6

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3

(a) Question 3 (a) provides you with a logic diagram and asks you to complete a truth table. This diagram contains an XOR gate a NOR and a NAND so be sure to take your time when completing the table.
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​(b) Part B asks you to explain the difference between an AND and a OR gate. The question is worth 3 marks. Each of the following points are worth 1 mark (Max 3)

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  • output of AND is 1 if both inputs are 1
  • output of AND is 0 if either or both inputs are 0
  • output of OR is 1 if either input is 1
  • output of OR is 0 if both inputs are 0
  • Correct example of AND truth table
  • Correct example of OR truth table