Twenty Questions

Electronics

Twenty Questions

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

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.

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

• 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.

15. Name 3 output devices

•Relay, loudspeaker,•Light bulb, LED, Heater,•Buzzer

16. What happens to the value of V2 as R1 increases?

• V2 decreases0V

10V

V2

R1

R2

17. If R1=10kΩ and R2=2.5kΩ calculate V2.

0V

10V

V2

VV

V

VRR

RV s

2

10250010000

2500

2

2

21

22

18. Which component is used for a time delay?

• Capacitor.

Vol

tage

19. Draw a circuit showing which way an LED should be connected to a battery

+ -

20. Give the energy change for the following.

LED Solenoid RelayLoudspeaker

Electrical LightElectrical KineticElectrical KineticElectrical Sound