Transcript N45 Electronics 20Q

Twenty Questions
Electronics
Twenty Questions
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20
1. At the start of the experiment,
the ammeter reading is 0.02A, at
the end it is 0.15A
T
A
Explain whether the resistance of the component
shown has increased or decreased.
• Resistance decreases as
the current increases.
• I=V/R, where V is
constant.
2. Of what 3 main parts does an
electronic system consist?
• Input
• Process
• Output
3. Name the component &
explain how it works.
• Thermistor
• Temperature
Up
Resistance
Down
4. Select suitable input and output
devices for a baby monitor.
• Input – Microphone
• Output - Loudspeaker
5. Give 3 input devices
Light sensor, solar cell, LDR,
Thermistor, Microphone,
Thermocouple, switch
• Dimmer switch.
• Volume control on radio.
• Heat dial on cooker.
6. What does an electrical relay do?
• Switches on and off a
separate electrical
circuit which might
have high current or
voltage.
7. Name & state the
function of the component.
• Transistor
• Electronic switch
which automatically
switches ON at 0.7V.
8. Why would you use an LED instead
of a filament to indicate that an
electrical appliance was switched on?
• Less heat produced.
• Lower energy usage.
• Smaller.
9V
9. Calculate the current if
the light level is 25lux.
• I = V/R
• I = 9/60
• I = 0.15A
A
Light level Resistance
15
120
20
80
25
60
10. How can you decrease the time
delay in a capacitor/resistor circuit?
• Decrease the value of
the capacitor
• Decrease the value of
the resistor.
11. Name the component
& explain how it works.
• LDR (light dependent resistor)
• Light
Up
Resistance
Down
12. Give the energy change for the
following.
Solar cell
Microphone
Thermistor
LDR
Light
Sound
Heat
Light
Electrical
Electrical
Electrical
Electrical
13. The LED has a voltage
2V. What is the value of R?
• VR = 12-2 =10V
• R = VR / I
= 10/2.5
= 4Ω
12V
2.5A
R
14. Why is a resistor always put in
series with an LED?
• To limit the current
so the LED does not
melt.
15. Name 3 output devices
•Relay, loudspeaker,
•Light bulb, LED, Heater,
•Buzzer
10V
16. What happens to the
value of V2 as R1 increases?
• V2 decreases
R1
R2
0V
( This is because as R1
increases the voltage across
it, V1, increases. As the total
voltage remains the same, V2
must decrease.)
V2
10V
17. If R1=10kΩ and R2=2.5kΩ
calculate V2.
V2
0V
 R2 
Vs
V2  
 R1  R2 
2500


V2  
10
 10000  2500 
V2  2V
• Capacitor.
Voltage
18. Which component is
used for a time delay?
19. Draw a circuit showing which way
an LED should be connected to a
battery
+
-
20. Give the energy change for the
following.
Electrical
LED
Electrical
Solenoid
Electrical
Relay
Loudspeaker Electrical
Light
Kinetic
Kinetic
Sound