Ministry of Education
Secondary Engagement Programme
Grade 11
Physics
WEEK 8
Lessons - Worksheet
1. Which gate is called an inverter?
(A) AND
(B) OR
(C) NOR
2. What is the name of the gate shown in the diagram?
(A) AND
(B) OR
(C) NAND
(D) NOT
(D) NOR
3. Complete the truth table for the combination of gates shown in figure below:
4. The diagram shows a light-emitting diode (LED) and a
buzzer connected to a 6.0 V power supply.
(i)
For which position of the switch will the LED
light? Explain your answer.
(ii)
What is the name given to the component labelled
E, and what is its function in the circuit?
(iii)
If the current through the LED is not to exceed 20
mA, calculate the minimum value required for E.
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Ministry of Education
Secondary Engagement Programme
Grade 11
Physics
5. Complete the truth table for the combined gates shown in the diagram.
Truth table for Question 5.
i.
ii.
iii.
Which combination(s) produce(s) a logic 1 output in Y 3?
Suggest a possible practical use of this type of circuit .
6. Identify the logic gates described in the first column of the table below and hence
complete the table by writing in the names and logic symbols in the appropriate columns.
a.
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Ministry of Education
Secondary Engagement Programme
Grade 11
Physics
Examine the logic circuit shown in Figure 2 and complete the TRUTH TABLE below:
c. The logic circuit of Figure 2 is incorporated into the electrical system of a car as
shown in Figure 3 below and switches S I and S2 are operated according to the table
below.
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Ministry of Education
Secondary Engagement Programme
Grade 11
Physics
Figure 3
Explain what happens if:
(i)
(ii)
the DOOR is OPEN and the ENGINE is OFF.
(ii) the DOOR is OPEN and the ENGINE is ON.
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Ministry of Education
Secondary Engagement Programme
Grade 11
Physics
WEEK 8
Lesson: Worksheet - Answers
1. D
2. C
3.
4. i) Y. The orientation of the diode is such that the current will easily pass through the
diode to Y on its way to 0V. (The buzzer has a higher resistance than the wire and
therefore most of the current will pass through the wire from Y and very little through the
buzzer)
(ii) Resistor. To limit the current through the diode and thus to protect the diode from
excessive heating
(iii) 300Ω
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Ministry of Education
Secondary Engagement Programme
Grade 11
Physics
5.
ii. All combinations except the last row: A–1, B–1, and C–1
(iii) If any of three circuits with outputs to A, B, and C are not working (i.e. a logic output of 0),
a warning light (Y3 ) goes on.
Thus the logic circuit can be used to monitor if any of the three circuits is/are not functioning
6. A.
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Ministry of Education
Secondary Engagement Programme
Grade 11
Physics
b.
A
0
0
1
1
B
0
1
0
1
W
1
1
0
0
X
0
0
0
0
Y
0
1
0
0
c. i. If the door is open and the engine is off:
Alarm 2 will sound because A is at “0” state and B is at “1” state.
Hence, the input at W will be “1” Since the NOT gate inverts the “0”.
Output Y is the output of an AND gate, and since both inputs are high, the high will
sound.
c. ii. If the door is open and the engine is on:
Alarm 1 will sound because A is at “1” state and B is at “1” state. Hence, input at W will
be “0”, since the NOT gate inverts the “1”.
Output Y is the output of an AND gate, and since both inputs ate not high, alarm 2 will
not sound. B is also the input of the output X.
X, is also the output of the AND gate, and since A is “1”, both in
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