A burglar-alarm system in a house sounds an alarm during the hours of darkness when one of the following conditions is met: - the door is open - the window is opened - both the door and the window are opened. Figure 5 shows the main burglar-alarm subsystems and the logic status for the inputs and output. Complete Table 2. Inputs | C | B | A | Q ----------|----|----|----|---- | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 Table 2 is a partially completed truth table for the logic subsystem.

A-Level AQA Physics Current–Voltage Characteristics: A burglar-alarm system in a hous

A burglar-alarm system in a house sounds an alarm during the hours of darkness when one of the following conditions is met: - the door is open - the window is opened - both the door and the window are opened - AQA - A-Level Physics - Question 2 - 2021 - Paper 8

Question 2

A burglar-alarm system in a house sounds an alarm during the hours of darkness when one of the following conditions is met: - the door is open - the window is opene... show full transcript

Worked Solution & Example Answer:A burglar-alarm system in a house sounds an alarm during the hours of darkness when one of the following conditions is met: - the door is open - the window is opened - both the door and the window are opened - AQA - A-Level Physics - Question 2 - 2021 - Paper 8

Step 1

Complete Table 2:

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C	B	A	Q
0	0	0	0
0	0	1	1
0	1	0	1
0	1	1	1
1	0	0	1
1	0	1	0
1	1	0	1
1	1	1	1

Step 2

Complete Figure 7:

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To connect the switch in Figure 6 with a 10 kΩ resistor:

Connect the switch in series with the resistor.
The input terminal connects to the 9 V supply.
The output will be taken across the resistor, marked with an X.

Step 3

Write the Boolean algebra expression for Q in terms of inputs A, B and C:

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The expression for Q using only AND and NOR operators is given by:

$Q = (C' ext{ AND } (B' ext{ AND } A))$

Where ' indicates NOT operation.

Step 4

State the logic function performed by gate 4:

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Answer

Gate 4 acts as an inverter, meaning it outputs the opposite value of its input.

Step 5

Suggest why:

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The reason for using one type of logic gate instead of two could be:

Using only one type may reduce the complexity of the circuit, leading to a more compact design.
It may help in minimizing costs, as only one type of chip is needed to produce the circuit.

A burglar-alarm system in a house sounds an alarm during the hours of darkness when one of the following conditions is met: - the door is open - the window is opened - both the door and the window are opened - AQA - A-Level Physics - Question 2 - 2021 - Paper 8

Worked Solution & Example Answer:A burglar-alarm system in a house sounds an alarm during the hours of darkness when one of the following conditions is met: - the door is open - the window is opened - both the door and the window are opened - AQA - A-Level Physics - Question 2 - 2021 - Paper 8

Complete Table 2:

Complete Figure 7:

Write the Boolean algebra expression for Q in terms of inputs A, B and C:

State the logic function performed by gate 4:

Suggest why:

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