twenty questions electronics. twenty questions 12345 678910 1112131415 1617181920
TRANSCRIPT
1. At the start of the experiment, the ammeter reading is 0.02A, at the end it is 0.15A
• Resistance has decreased as the current has increased. • I=V/R, where V is constant.
T A
Explain whether the resistance of the component show has increased or decreased.
4. Select suitable input and output devices for a baby monitor.
• Input – Microphone• Output - Loudspeaker
5. Give 3 input devices
• Dimmer switch.• Volume control on radio.• Heat dial on cooker.
Light sensor, solar cell, LDR, Thermistor, Microphone, Thermocouple, switch
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.
9. Calculate the current if the light level is 25lux.
• I = V/R• I = 9/60• I = 0.15A
A
9V
Light level Resistance
15 120
20 80
25 60
10. How can the frequency of a clock pulse generator be increased?
• 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 MicrophoneThermistorLDR
Light Electrical Sound Electrical Heat ElectricalLight 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.