The NOR gate

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The NOR gate

Name:
Date:
Class:
A

Quick Questions

Shade in the A or B circle for each question.

1. A NOR gate has two inputs, A and B. When is the output X equal to 1?
A Only when A = 0 and B = 0
B When A = 1 or B = 1
2. Which output column (for A,B = 00, 01, 10, 11) is correct for a NOR gate?
A 0 1 1 1
B 1 0 0 0
3. Which symbol shows a NOR gate?
A The AND symbol with a small circle on the output
B The OR symbol with a small circle on the output
4. Which expression describes a NOR gate?
A X = NOT (A OR B)
B X = (NOT A) OR B
5. A NOR gate has inputs A = 1 and B = 0. What is the output X?
A 0
B 1
B

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left columnRight column
1X = A NOR B AX = NOT (A OR B)
2A = 0, B = 0, X = 1 B1 0 0 0
3NOR is OR followed by NOT, so the result of the OR is flipped CA NOR gate outputs 0 when any input is 1. With A = 1 and B = 0, X should be 0.
4The NOR output column for input rows 00, 01, 10 and 11, in that order DThe NOR gate: two inputs A and B, one output X, which is the opposite of OR
5X = NOT (A AND B) EThe only row where a NOR gate outputs 1: both inputs are 0
6A = 1, B = 0, X = 1 FThis is NAND, not NOR. NOR needs OR inside the brackets: X = NOT (A OR B).
C

Definitions

X = NOT (A OR B)
D

Fill in the Blanks

Complete each line of code by filling in the missing parts.

1.
X = NOT (A __ B)
2.
X = ___ (A OR B)
3.
X = A ___ B
4.
When A = 0 and B = 0, X = _
5.
Symbol: OR with a small ______ on output
E

Spot the Error

Shade in the letter of the line that contains an error.

Question 1
A A B | X
B 0 0 | 1
C 0 1 | 1
D 1 0 | 0
E 1 1 | 0
Question 2
A A = 0
B B = 0
C X = NOT (A AND B)
D OUTPUT X
Question 3
A NOR is AND followed by NOT
B X = NOT (A OR B)
C A = 1, B = 0
D X is 0
Question 4
A A B | X (NOR gate)
B 1 1 | 1
C 1 0 | 0
D 0 0 | 1
Question 5
A X = NOT A OR B
B A = 0
C B = 1
D OUTPUT X

Answer Key

The NOR gate
Section A: Quick Questions
Q1
A — Only when A = 0 and B = 0
Q2
B — 1 0 0 0
Q3
B — The OR symbol with a small circle on the output
Q4
A — X = NOT (A OR B)
Q5
A — 0
Section B: Match the Pairs
Q1
X = A NOR B → The NOR gate: two inputs A and B, one output X, which is the opposite of OR
Q2
A = 0, B = 0, X = 1 → The only row where a NOR gate outputs 1: both inputs are 0
Q3
NOR is OR followed by NOT, so the result of the OR is flipped → X = NOT (A OR B)
Q4
The NOR output column for input rows 00, 01, 10 and 11, in that order → 1 0 0 0
Q5
X = NOT (A AND B) → This is NAND, not NOR. NOR needs OR inside the brackets: X = NOT (A OR B).
Q6
A = 1, B = 0, X = 1 → A NOR gate outputs 0 when any input is 1. With A = 1 and B = 0, X should be 0.
Section C: Definitions
Q1
X = NOT (A OR B) — The NOR gate: output X is 1 only when both inputs A and B are 0. It is OR followed by NOT, so the truth table output is 1 0 0 0. Its symbol is OR with a small circle.
Section D: Fill in the Blanks
Q1
X = NOT (A OR B)
Q2
X = NOT (A OR B)
Q3
X = A NOR B
Q4
When A = 0 and B = 0, X = 1
Q5
Symbol: OR with a small circle on output
Section E: Spot the Error
Q1
C — A NOR gate outputs 1 only when both inputs are 0. When A is 0 and B is 1, the output must be 0, so the line should be 0 1 | 0.
Q2
C — NOR is OR followed by NOT. NOT (A AND B) is the NAND gate. The line should be X = NOT (A OR B).
Q3
A — NOR is OR followed by NOT. AND followed by NOT would be NAND. The line should say NOR is OR followed by NOT.
Q4
B — A NOR gate gives 0 whenever at least one input is 1. With A = 1 and B = 1 the output is 0, so the line should be 1 1 | 0.
Q5
A — Without brackets, NOT applies only to A. NOR needs NOT to apply to the whole OR result, so the line should be X = NOT (A OR B).