Computer Science: Logic Gates Worksheet

Question 1

Complete the truth table for an AND gate with inputs A and B. List the output for A,B values 00, 01, 10, and 11.

Accepted Answer

The AND gate outputs 0 for 00, 0 for 01, 0 for 10, and 1 for 11. An AND gate only outputs 1 when both inputs are 1.

Question 2

Complete the truth table for an OR gate with inputs A and B. List the output for A,B values 00, 01, 10, and 11.

Accepted Answer

The OR gate outputs 0 for 00, 1 for 01, 1 for 10, and 1 for 11. An OR gate outputs 1 when at least one input is 1.

Question 3

Complete the truth table for a NOT gate with input A. List the output for A values 0 and 1.

Accepted Answer

The NOT gate outputs 1 when A is 0 and outputs 0 when A is 1. A NOT gate reverses the input.

Question 4

A circuit has inputs A = 1 and B = 0 connected to an AND gate. What is the output? Explain your answer.

Accepted Answer

The output is 0 because an AND gate requires both inputs to be 1, and B is 0.

Question 5

A circuit has inputs A = 1 and B = 0 connected to an OR gate. What is the output? Explain your answer.

Accepted Answer

The output is 1 because an OR gate outputs 1 when at least one input is 1, and A is 1.

Question 6

A circuit first sends input A through a NOT gate, then sends the result and input B into an AND gate. If A = 0 and B = 1, what is the final output?

Accepted Answer

The NOT gate changes A = 0 into 1. Then the AND gate receives 1 and 1, so the final output is 1.

Question 7

Write the Boolean expression for a circuit where inputs A and B go into an AND gate, and the result is inverted by a NOT gate.

Accepted Answer

The Boolean expression is NOT (A AND B), often written as ¬(A ∧ B) or (A AND B)'. This circuit is a NAND gate.

Question 8

A NAND gate is the opposite of an AND gate. Complete the NAND output for A,B values 00, 01, 10, and 11.

Accepted Answer

The NAND gate outputs 1 for 00, 1 for 01, 1 for 10, and 0 for 11. It is only 0 when both inputs are 1.

Question 9

A NOR gate is the opposite of an OR gate. Complete the NOR output for A,B values 00, 01, 10, and 11.

Accepted Answer

The NOR gate outputs 1 for 00, 0 for 01, 0 for 10, and 0 for 11. It is only 1 when both inputs are 0.

Question 10

An XOR gate outputs 1 when exactly one input is 1. Complete the XOR output for A,B values 00, 01, 10, and 11.

Accepted Answer

The XOR gate outputs 0 for 00, 1 for 01, 1 for 10, and 0 for 11. It outputs 1 only when the inputs are different.

Question 11

A circuit computes (A OR B) AND C. If A = 0, B = 1, and C = 1, what is the output?

Accepted Answer

First, A OR B equals 1 because B is 1. Then 1 AND C equals 1, so the final output is 1.

Question 12

A circuit computes A AND (NOT B). If A = 1 and B = 1, what is the output?

Accepted Answer

NOT B changes B = 1 into 0. Then A AND 0 equals 0, so the final output is 0.

Question 13

For the expression (A AND B) OR (A AND C), find the output when A = 1, B = 0, and C = 1.

Accepted Answer

A AND B equals 0 because B is 0. A AND C equals 1 because both A and C are 1. Then 0 OR 1 equals 1, so the output is 1.

Question 14

A security light should turn on only when it is night and motion is detected. Let N = 1 mean it is night, and M = 1 mean motion is detected. Which logic gate should be used, and why?

Accepted Answer

An AND gate should be used because the light should turn on only when both N and M are 1.

Question 15

A warning buzzer should turn on if a door is open or a window is open. Let D = 1 mean the door is open, and W = 1 mean the window is open. Which logic gate should be used, and why?

Accepted Answer

An OR gate should be used because the buzzer should turn on when either D is 1, W is 1, or both are 1.

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Computer Science: Logic Gates

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