Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 491 · 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 home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
2. 2.⚡ A 3 W device works on 12 V. What current does it take (in amperes)? =
3. 3.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 5300 Ω resistor? (a) green-orange-red (b) green-orange-brown (c) orange-green-red (d) green-orange-orange
4. 4.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
5. 5.🌈 A resistor has the colour bands violet, yellow, black. What is its value (in ohms)?
6. 6.Which of these saves electricity? (a) leave fridge door open (b) set the AC to 24 °C (c) use old filament bulbs (d) iron one shirt at a time
7. 7.What does a thermistor do? (a) turns a fan or wheels (b) senses how hot it is (c) makes a beeping sound (d) beeps for an alarm
8. 8.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 100 (c) 1000 (d) 60
9. 9.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
10. 10.True or false: a diode lets current go one way. (a) True (b) False
11. 11.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
12. 12.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
13. 13.True or false: the flow of charge is measured in amperes (A). (a) False (b) True
14. 14.🧮 A 1.2 V battery is joined to 3 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
15. 15.💡 Does it save or waste electricity to unplug idle chargers? (a) saves electricity (b) wastes electricity
16. 16.Which of these is measured in watts (W)? (a) resistance (b) power (c) current (d) how much a part resists
17. 17.📏 Which unit measures the flow of charge? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
18. 18.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =
19. 19.🌈 A resistor has the colour bands green, black, yellow. What is its value in kilo-ohms (kΩ)? =
20. 20.🔺 A current of 0.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 21000 Ω resistor? (a) brown-red-orange (b) red-brown-yellow (c) red-brown-orange (d) red-brown-red
22. 22.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🧮 A 47 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
24. 24.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
25. 25.🔺 An 18.8 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
26. 26.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
27. 27.📏 How many ohms (Ω) is 3 kΩ?
28. 28.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =
29. 29.True or false: on an LED, the round-side leg is the anode (+). (a) False (b) True
30. 30.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
31. 31.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) smaller (c) zero (d) bigger
32. 32.🔺 A 1 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
33. 33.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🧩 Which component turns a fan or wheels? (a) diode (b) LDR (c) motor (d) capacitor
35. 35.🔺 A current of 3 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.⚡ A 1.25 W device works on 5 V. What current does it take (in amperes)? =
37. 37.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
38. 38.🔺 A current of 40 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
39. 39.⚡ A 0.5 W device works on 5 V. What current does it take (in amperes)? =
40. 40.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?

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