Electronics Worksheet: Final Test

Electronics lesson 30: Final electronics test · Set 259 · 40 questions

Remember (Find the topic, use the idea): Find the topic: circuit, safety, formula, component, program, sensor or IoT. Use that lesson’s rule — complete loop, V = I × R, P = V × I, last command wins, true → if part. Safety answers are always: low voltage, dry hands, an adult, never the mains.

1. 1.🔍 An object is 34 cm from a distance sensor. Sound travels about 34 cm every millisecond. After how many milliseconds does the echo come back?
2. 2.💡 An LED (with its resistor) is on pin 8. All pins start LOW. The program runs once:
   set pin 7 LOW
   set pin 8 HIGH
   set pin 8 LOW
   set pin 8 HIGH
   set pin 7 HIGH
   Is the LED ON or OFF at the end? (a) ON (b) OFF
3. 3.Which of these saves electricity? (a) use old filament bulbs (b) run fans in empty rooms (c) use daylight to read (d) leave fridge door open
4. 4.💡 6 identical bulbs are joined in series with a battery and a closed switch on the main wire. Bulb 2 is taken out of its holder. How many bulbs glow?
5. 5.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 2.75 V supply. What current flows (in mA)?
6. 6.🔍 Which is the odd one out? (a) a light sensor (b) a servo motor (c) a motor (d) a water pump
7. 7.Which drawing is the symbol for a cell? (a) a small empty box (b) a long and a short line (c) two equal parallel lines (d) a circle with a cross
8. 8.🔢 To run one loop of a plant-watering program, what comes right after “read the soil sensor”? (a) wait a few seconds (b) switch the pump on/off (c) compare with the limit
9. 9.💡 In a series circuit, how many paths does the current have? (a) one for each bulb (b) one (c) two (d) none
10. 10.🔁 Is the circuit closed or open if a cell is taken out? (a) open (b) closed
11. 11.🔺 A current of 25 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
12. 12.✏️ Why do engineers draw circuits with symbols? (a) symbols are heavier (b) to make it colourful (c) quick and clear for all (d) to hide the circuit
13. 13.🧩 Which component lets current go one way? (a) resistor (b) motor (c) transistor (d) diode
14. 14.🤖 Which is a safe power source for a beginner microcontroller board? (a) USB or a 9 V battery (b) a 230 V cable (c) a wall socket directly (d) bare mains wires
15. 15.🔋 5 identical 1.5 V cells are joined in series, but one of them is put in the wrong way round. What is the total voltage now (in volts)? =
16. 16.🔍 Which is the odd one out? (a) open a phone charger (b) stop if a part gets hot (c) poke things in a socket (d) touch a switch when wet
17. 17.💡 4 identical bulbs are joined in parallel across a 1.5 V battery (ideal wires). How many volts does each bulb get? =
18. 18.True or false: a buzzer limits the current. (a) False (b) True
19. 19.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) smaller (c) stay the same (d) bigger
20. 20.⏱️ repeat 9 times { buzzer ON; wait 400 ms; buzzer OFF; wait 600 ms }
    How many milliseconds does this take in all?
21. 21.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 25 % (d) 0 %
22. 22.Which of these saves electricity? (a) run fans in empty rooms (b) leave the TV on standby (c) leave fridge door open (d) use LED lamps
23. 23.🔍 Which sensor would you use to switch on with a clap? (a) a gas sensor (b) a temperature sensor (c) a sound sensor (d) a distance sensor
24. 24.🔍 Which is the odd one out? (a) use daylight to read (b) run fans in empty rooms (c) switch off empty rooms (d) set the AC to 24 °C
25. 25.🔋 How many 3 V cells must be joined in series to give 24 V?
26. 26.🔺 A 36 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
27. 27.🔐 Is it a good or a risky habit to cover unused cameras? (a) good habit (b) risky habit
28. 28.🔁 repeat 5 times { repeat 3 times { beep } }
    How many beeps are there?
29. 29.🤖 Does a toy robot usually have a microcontroller inside? (a) No (b) Yes
30. 30.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to store charge (d) to limit the current
31. 31.💡 A battery lights 2 identical bulbs joined in parallel. One more identical bulb is added in parallel. How do the bulbs glow now? (a) dimmer (b) brighter (c) the same
32. 32.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) the gold band (d) any band
33. 33.🔦 A tester circuit has a new cell, a good bulb and wires with a gap between two clips. We put a rubber eraser across the gap. Does the bulb glow? (a) Yes (b) No
34. 34.🔍 Which is the odd one out? (a) stay away from pylons (b) keep drinks far away (c) dry your hands first (d) touch a fallen wire
35. 35.True or false: a copper wire is a conductor. (a) False (b) True
36. 36.🔘 A cell, a bulb and switches A, B and C are joined one after another in a single loop (series). A is OFF, B is OFF and C is OFF. Does the bulb glow? (a) No (b) Yes
37. 37.🔍 Which is the odd one out? (a) change default passwords (b) keep factory passwords (c) cover unused cameras (d) install software updates
38. 38.🌈 A resistor has the colour bands orange, grey, black. What is its value (in ohms)?
39. 39.🔌 Is a metal paper clip a conductor or an insulator? (a) an insulator (b) a conductor
40. 40.True or false: “how bright a room is” is a digital signal. (a) False (b) True

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