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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 855 · 40 questions
TalentJR

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.

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  1. 1.⚡ An 18 W device works on 12 V. What current does it take (in amperes)? =
  2. 2.🔺 A current of 2 A flows when 16 V is joined across a resistor. What is its resistance (in ohms)?
  3. 3.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
  4. 4.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = I ÷ V (c) R = V × I (d) R = V + I
  5. 5.🌈 Which band is read first on a resistor? (a) the widest gap (b) any band (c) the one nearest an end (d) the gold band
  6. 6.True or false: to run fans in empty rooms saves electricity. (a) False (b) True
  7. 7.🔺 A current of 2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.⚡ Which formula gives electric power? (a) P = V × I (b) P = V + I (c) P = I ÷ V (d) P = V ÷ I
  9. 9.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
  10. 10.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 100 (b) 10 (c) 1024 (d) 1000
  11. 11.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a resistor (c) a capacitor (d) a diode
  12. 12.⚡ A 5 W device works on 5 V. What current does it take (in amperes)? =
  13. 13.🧮 A 1.6 V battery is joined to 8 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
  14. 14.True or false: to unplug idle chargers wastes electricity. (a) True (b) False
  15. 15.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V + R (c) I = V × R (d) I = V ÷ R
  16. 16.🧩 Which component blows if current is high? (a) fuse (b) thermistor (c) resistor (d) potentiometer
  17. 17.True or false: the ammeter is joined across a part. (a) False (b) True
  18. 18.🔺 A 2.2 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
  19. 19.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the colour of light (d) the size of a cell
  20. 20.🧾 A 100 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
  21. 21.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  22. 22.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  23. 23.🌈 A resistor has the colour bands brown, orange, black. What is its value (in ohms)?
  24. 24.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  25. 25.What does a fuse do? (a) blows if current is high (b) stores a little charge (c) senses how bright it is (d) lets current go one way
  26. 26.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 10 (d) 1000
  27. 27.🌈 A resistor has the colour bands orange, white, red. What is its value (in ohms)?
  28. 28.🔺 A 4.8 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  29. 29.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
  30. 30.Which of these saves electricity? (a) run fans in empty rooms (b) leave the TV on standby (c) close the fridge quickly (d) leave fridge door open
  31. 31.True or false: an LED glows using little power. (a) False (b) True
  32. 32.What does a diode do? (a) lets current go one way (b) is a resistance knob (c) senses how hot it is (d) boosts a small signal
  33. 33.💡 Does it save or waste electricity to use daylight to read? (a) saves electricity (b) wastes electricity
  34. 34.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
  35. 35.🔺 A 12 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  36. 36.🔺 A current of 50 mA flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  37. 37.🧮 Resistors of 22 Ω, 10 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
  38. 38.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  39. 39.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
  40. 40.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. 1.5
  2. 8
  3. saves electricity
  4. R = V ÷ I
  5. the one nearest an end
  6. False
  7. 4
  8. P = V × I
  9. wastes electricity
  10. 1000
  11. a buzzer
  12. 1
  13. 0.1
  14. False
  15. I = V ÷ R
  16. fuse
  17. False
  18. 10
  19. energy used each second
  20. 0.2
  21. 100
  22. 150
  23. 13
  24. cathode (−)
  25. blows if current is high
  26. 1000
  27. 3900
  28. 40
  29. True
  30. close the fridge quickly
  31. True
  32. lets current go one way
  33. saves electricity
  34. saves electricity
  35. 1.5
  36. 300
  37. 362
  38. 500
  39. voltmeter
  40. 7.5

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