Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 722 · 40 questions

Remember (Find the topic, use the formula): Find the topic and the formula: V = I × R, I = V ÷ R, R = V ÷ I, P = V × I, units = W × h ÷ 1000. Change mA to A and kΩ to Ω before using a formula. Check: put your answer back into the formula.

1. 1.What does an LED do? (a) glows using little power (b) smooths a wobbly supply (c) lets current go one way (d) beeps for an alarm
2. 2.🌈 Which band is read first on a resistor? (a) the gold band (b) any band (c) the one nearest an end (d) the widest gap
3. 3.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
4. 4.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) smaller (c) stay the same (d) bigger
5. 5.🧩 Which component lets current go one way? (a) thermistor (b) transistor (c) resistor (d) diode
6. 6.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.🧮 An 11 V battery is joined to 12 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
8. 8.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I ÷ R (c) V = I + R (d) V = I × R
9. 9.Which of these wastes electricity? (a) switch off empty rooms (b) set the AC to 24 °C (c) close the fridge quickly (d) leave the TV on standby
10. 10.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
11. 11.Which of these is measured in ohms (Ω)? (a) the push of a cell (b) how much a part resists (c) current (d) the flow of charge
12. 12.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
13. 13.True or false: a resistor glows using little power. (a) True (b) False
14. 14.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
15. 15.What does an LDR do? (a) beeps for an alarm (b) has coloured bands (c) senses how bright it is (d) stores a little charge
16. 16.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V ÷ I (d) P = V + I
17. 17.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
18. 18.What does a buzzer do? (a) blows if current is high (b) makes a beeping sound (c) boosts a small signal (d) senses how bright it is
19. 19.💡 A red LED uses 2 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
20. 20.🔺 A current of 25 mA flows when 6.25 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
22. 22.🔺 A current of 10 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🔺 A current of 0.2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
25. 25.⚡ A device works on 6 V and takes 2 A. What is its power (in watts)? =
26. 26.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 71 Ω resistor? (a) brown-violet-black (b) violet-brown-brown (c) grey-brown-black (d) violet-brown-black
27. 27.🔺 A current of 0.1 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.🧩 Which component blows if current is high? (a) resistor (b) potentiometer (c) fuse (d) thermistor
29. 29.⚡ A device works on 24 V and takes 0.1 A. What is its power (in watts)? =
30. 30.Which of these is measured in amperes (A)? (a) voltage (b) resistance (c) the flow of charge (d) the push of a cell
31. 31.🔺 A current of 2 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
32. 32.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
33. 33.True or false: to leave fridge door open wastes electricity. (a) False (b) True
34. 34.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
35. 35.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 99 Ω resistor? (a) brown-white-black (b) white-white-brown (c) white-black-black (d) white-white-black
36. 36.🔺 A current of 0.1 A flows when 0.6 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
38. 38.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
39. 39.🔺 A current of 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?

Free electronics lessons, practice and worksheets at talentjr.in/electronics-for-kids