Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 27 · 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.Which of these saves electricity? (a) switch off empty rooms (b) iron one shirt at a time (c) leave the TV on standby (d) leave fridge door open
2. 2.🔺 An 8 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
3. 3.🧩 Which component stores a little charge? (a) buzzer (b) resistor (c) capacitor (d) thermistor
4. 4.🌈 A resistor has the colour bands red, red, red. What is its value (in ohms)?
5. 5.🔺 A current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
6. 6.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) measure heat (d) store charge briefly
8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 7200 Ω resistor? (a) violet-red-brown (b) red-violet-red (c) violet-red-red (d) violet-red-orange
9. 9.🔺 A current of 10 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
10. 10.Which of these saves electricity? (a) run fans in empty rooms (b) close the fridge quickly (c) iron one shirt at a time (d) leave fridge door open
11. 11.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
12. 12.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) smaller (d) stay the same
13. 13.True or false: a potentiometer makes things spin. (a) True (b) False
14. 14.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
15. 15.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
16. 16.🧮 Resistors of 50 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
17. 17.🧮 A 1.2 V battery is joined to 4 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
18. 18.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
19. 19.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
20. 20.🌈 A resistor has the colour bands red, green, yellow. What is its value in kilo-ohms (kΩ)? =
21. 21.True or false: resistance is measured in ohms (Ω). (a) True (b) False
22. 22.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = V × I (d) P = I ÷ V
23. 23.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
24. 24.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.🔺 A 20 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
26. 26.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
27. 27.🔺 A 4.8 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
28. 28.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 5 V supply. What current flows (in mA)?
29. 29.🔺 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
30. 30.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
31. 31.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
32. 32.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
33. 33.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
34. 34.True or false: a fuse makes a beeping sound. (a) False (b) True
35. 35.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
36. 36.🔺 A current of 25 mA flows when 8.25 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 420 Ω resistor? (a) red-yellow-brown (b) yellow-red-black (c) yellow-red-brown (d) yellow-red-red
38. 38.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
39. 39.True or false: an LED limits the current. (a) True (b) False
40. 40.📏 Which unit measures voltage? (a) ohm (Ω) (b) volt (V) (c) ampere (A) (d) watt (W)

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