Worksheet: OR Gates

In this worksheet, we will practice determining the input and output of OR gates in logic circuits and completing truth tables for OR gates.

Q1:

The diagram shows the circuit symbols for four logic gates. Which symbol represents an OR gate?

  • A(b)
  • B(c)
  • C(d)
  • D(a)

Q2:

The diagram shows an OR gate. If input A is 0 and the output is 0, what must input B be?

Q3:

The truth table shows the output of an OR gate for various combinations of inputs.

OR Gate
Input AInput BOutput
000
01𝑝
101
11𝑞

What is the value of 𝑝 in the table?

What is the value of 𝑞 in the table?

Q4:

A logic circuit has 4 inputs, each of which can have a value of either 0 or 1. How many rows would you have to add to a truth table in order to show all of the different possible combinations of these inputs?

Q5:

The diagram shows an OR gate. If input A is 1 and input B is 0, what will the output be?

Q6:

The diagram shows two OR gates, where the output of the first OR gate is one of the inputs to the second. If input A is 0, input B is 0, and input C is 1, what is the output?

Q7:

The diagram shows two OR gates connected as part of a logic circuit. The truth table shows the output for the various combinations of inputs.

Input AInput BInput COutput
0000
00𝑝1
0101
011𝑞
𝑟001
1011
110𝑠
1111

What is the value of 𝑝 in the table?

What is the value of 𝑞 in the table?

What is the value of 𝑟 in the table?

What is the value of 𝑠 in the table?

Q8:

The diagram shows a logic circuit consisting of three OR gates. How many different possible combinations of input values are there for this circuit?

Q9:

The diagram shows a logic circuit consisting of three OR gates. How many of the inputs must have a value of 0 in order for the output to have a value of 0?

Q10:

The diagram shows a logic circuit consisting of three OR gates. How many of the inputs must have a value of 1 in order for the output to have a value of 1?

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