Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 640 · 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.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
2. 2.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
3. 3.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
4. 4.🧮 A 14 V battery is joined to 2 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
5. 5.🔺 A current of 0.25 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
6. 6.📏 How many watts (W) is 2.6 kW?
7. 7.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V + I (d) P = V ÷ I
8. 8.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🔺 A 0.8 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
10. 10.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 10 Ω resistor? (a) brown-black-black (b) red-black-black (c) red-brown-black (d) brown-black-brown
11. 11.🔍 Which is the odd one out? (a) switch off empty rooms (b) use LED lamps (c) run fans in empty rooms (d) close the fridge quickly
12. 12.Which of these saves electricity? (a) leave the TV on standby (b) run fans in empty rooms (c) use old filament bulbs (d) unplug idle chargers
13. 13.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an oil lamp (c) an LED lamp (d) a candle
14. 14.True or false: how much a part resists is measured in ohms (Ω). (a) False (b) True
15. 15.🧮 Resistors of 33 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
16. 16.⚡ A 4.8 W device works on 24 V. What current does it take (in amperes)? =
17. 17.🧩 Which component has coloured bands? (a) capacitor (b) motor (c) diode (d) resistor
18. 18.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
19. 19.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
20. 20.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) any band (c) the widest gap (d) the gold band
21. 21.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 25 % (c) 50 % (d) 5 %
22. 22.🌈 A resistor has the colour bands green, violet, black. What is its value (in ohms)?
23. 23.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a diode (c) a resistor (d) a capacitor
24. 24.⚡ A 5 W device works on 5 V. What current does it take (in amperes)? =
25. 25.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
26. 26.True or false: on an LED, the round-side leg is the anode (+). (a) False (b) True
27. 27.⚡ A device works on 6 V and takes 1 A. What is its power (in watts)? =
28. 28.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
29. 29.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 95000 Ω resistor? (a) white-green-red (b) green-white-orange (c) white-green-orange (d) white-green-yellow
30. 30.🔺 A current of 40 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
31. 31.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
32. 32.🔺 A current of 0.25 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
33. 33.True or false: voltage is measured in watts (W). (a) True (b) False
34. 34.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it lights brighter (c) it changes colour (d) it does not light
35. 35.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.🔺 A 50 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
37. 37.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
39. 39.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?
40. 40.🔺 An 11.75 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?

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