Intermediate 1
Physics
Electronics
Questions
and
Answers
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Intermediate 1
Physics
Electronics
Q 1 to 9
Q 10 to 18
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Electronic Systems
1.
Describe what is meant by an electronic system. Give
two examples
An electronic system is made up from lots of
electronic components to do a particular job.
Two examples of electronic systems are a
calculator and a public address system.
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2. The block diagram for a calculator is shown
below.
Identify the input, process and output
subsystems.
Keypad
Calculating
Circuits
Input
Process
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Display
Output
4
3. Draw a block diagram of each of the following
systems. Identify the input, process and output
subsystems in each case.
(a)
A public address system
Input
microphone
(b)
Process
amplifier
Output
loudspeaker
A smoke alarm
Input
smoke
sensor
Process
logic
circuits
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Output
buzzer
5
(c) An automatic porch light (lamp lights when it gets dark)
Input
light
sensor
Process
Output
logic
circuits
bulb
(d) An automatic fan (fan operates when it gets too warm)
Input
temperature
sensor
Process
Output
logic
circuits
motor
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(e) A radio.
Input
aerial
Process
Output
amplifier
loudspeaker
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4. What is sensed by each of the following input devices
(a) microphone
(b) thermistor
sound
heat
(c) light dependent resistor light
(d) switch
pressure
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5. What can change the resistance of a thermistor?
Change in temperature
6. State how the resistance of a light dependent resistor
changes with light level.
As the light level increases the resistance decreases
7. Describe an experiment you would perform to determine
how the resistance of a thermistor changes with
temperature.
Connect a thermistor to a resistance meter and heat the
thermistor gently with your fingers. Watch what happens
to the resistance on the meter.
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8. Describe an experiment you would perform to determine
how the resistance of a light dependent resistor changes
with light level
Connect a LDR to a resistance meter and cover it over with
your hand. Watch what happens to the resistance on the
meter.
9. Describe how you would use an oscilloscope to examine
the output signal from a microphone. Describe what is
seen on the oscilloscope screen.
Connect the microphone to the input of the
oscilloscope. Speak into the microphone. You will see a
wave pattern on the screen which matches your voice.
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10. Describe the energy changes which take place in the
following output devices:
loudspeaker
electrical energy to sound energy
buzzer
electrical energy to sound energy
lamp
electrical energy to light energy
light emitting
diode (LED)
electrical energy to light energy
electric motor
electrical energy to kinetic energy
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11. Study the circuit symbols below. In each case:
(a) name the device
(b) state whether it is an input or output device
(c) state the energy changes in the device
(d) give an example of where it could be used
(a) microphone
(b) input device
device 1
(c) sound energy to electrical energy
(d) input to a public address system
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(a) buzzer
+
(b) output device
(c) electrical energy to sound energy
device 2
(d) warning device on a freezer, if
temperature inside rises above a
particular temperature
(a) motor
M
device 3
(b) output device
(c) electrical energy to kinetic energy
(d) output for a room cooling system
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(a) thermistor
(b) input device
(c) heat energy to electrical energy
device 4
(d) input device on a freezer, to check
temperature inside does not rises
above a particular temperature
(a) light emitting diode
(b) output device
(c) electrical energy to light energy
device 5
(d) indicates that something is switched on
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(a) lamp
(b) output device
(c) electrical energy to light energy
device 6
(d) output device for an automatic light
which switches on when it gets dark
(a) loudspeaker
(b) output device
device 7
(c) electrical energy to sound energy
(d) output device for a radio, so that we
can hear the music.
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(a) light dependent resistor
(b) input device
(c) light energy to electrical energy
device 8
(d) input device for an automatic light
which switches on when it gets dark
12. In the applications below identify which of
the devices in Q 11 would be suitable.
Give a reason for the choice of each device.
(a) Output of a radio
Loudspeaker, it changes the electrical energy
form the amplifier to sound energy
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(b) Input of an automatic lamp
LDR, because its resistance changes as the light
level changes
(c) Input of a heating controller
Thermistor, because its resistance changes as
the temperature changes
(d) Output of a fan
Motor, because it will turn the fan.
(e) Output of an electronic timer
Light emitting diode, it can form the part of a
seven segment display to show the numbers.
(f) Input of a cassette recorder – recorder subsystem
Microphone, it will pick up the sound to be recorded.
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(g) Output of a cassette recorder – drive subsystem.
Motor, it will turn the spindles.
(h) Output of a cassette recorder – play back system
Loudspeaker, it will change the electrical
energy back into sound energy.
13. Describe what is meant by a “digital signal”.
A digital signal is either on or off
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14. Draw an oscilloscope trace of a digital signal
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15. Draw the symbol for each of the following logic gates:
(a) NOT gate or Inverter
(b) AND gate
(c) OR gate
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16. The following is a truth table for a logic gate.
Input
Output
0
1
1
0
(a) Name the logic gate.
A NOT gate or inverter
(b) Explain in terms of voltage levels, what is meant by
the “1”s and “0”s.
“1” is a high voltage, “0” is a low voltage
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17. For each of the logic gates shown below:
(a) Name the gate
(b) Draw the truth table
(c) Describe the operation of the gate in words.
(a) NOT gate or inverter
Gate 1
(b)
Input
Output
0
1
1
0
(c) The output of the NOT gate is always the
opposite of the input
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A
B
(a) AND gate
Gate 2
(b)
Input A
Input B
Output
0
0
0
0
1
0
1
0
0
1
1
1
(c) The AND gate combines the input signals so
that the output is only 1 when both inputs are 1.
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A
B
(a) OR gate
Gate 3
(b)
Input A
Input B
Output
0
0
0
0
1
1
1
0
1
1
1
1
(c) The output of an OR gate is ‘1’ when any input is ‘1’.
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18. The system below is designed to allow water to be
sprayed on to plants if the air becomes too hot or the
gardener switches the sprayer on.
Heat
sensor
1 = hot
0 = cold
switch
A
Motor to
operate
sprayer
B
(a) Name the logic gate used in the system. OR gate
(b) The gardener switches the the sprayer on.
What is the logic level at B?
Logic 1
(c) What input device could be used in the heat sensor?
Thermistor
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Intermediate 1
Physics
Electronics
End of
Questions and
Answers
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