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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 734 · 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.🔺 A 6 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
  2. 2.🔺 A 12 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  3. 3.🔺 A current of 0.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.🧮 A 68 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  5. 5.🔍 Which is the odd one out? (a) run fans in empty rooms (b) use old filament bulbs (c) switch off empty rooms (d) leave fridge door open
  6. 6.🧮 Resistors of 220 Ω, 47 Ω, 100 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
  7. 7.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  8. 8.🔺 A current of 2 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  10. 10.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = I ÷ V (d) P = V + I
  11. 11.🧮 A 20 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  12. 12.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
  13. 13.🌈 In the resistor colour code, which number does violet stand for?
  14. 14.🧮 A 3 V battery is joined to 10 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
  15. 15.⚡ A 2.4 W device works on 12 V. What current does it take (in amperes)? =
  16. 16.Which of these wastes electricity? (a) close the fridge quickly (b) use daylight to read (c) unplug idle chargers (d) iron one shirt at a time
  17. 17.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
  18. 18.⚡ A device works on 3 V and takes 0.1 A. What is its power (in watts)? =
  19. 19.🧮 A 4 V battery is joined to 12 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
  20. 20.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
  21. 21.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  22. 22.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) the gold band (d) any band
  23. 23.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an LED lamp (c) a candle (d) an oil lamp
  24. 24.🔺 A current of 2.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  25. 25.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  26. 26.📏 How many kilowatts (kW) is 4800 W? =
  27. 27.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  28. 28.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.True or false: the voltmeter measures voltage. (a) True (b) False
  30. 30.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I × R (c) V = R ÷ I (d) V = I ÷ R
  31. 31.🔺 A current of 40 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.⚡ A device works on 5 V and takes 0.25 A. What is its power (in watts)? =
  33. 33.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 80000 Ω resistor? (a) grey-black-red (b) white-grey-orange (c) grey-black-yellow (d) grey-black-orange
  34. 34.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  35. 35.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to change its colour (d) to limit the current
  36. 36.🔺 A current of 1.5 A flows when 4.5 V is joined across a resistor. What is its resistance (in ohms)?
  37. 37.🔺 A current of 0.1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  38. 38.🌈 A resistor has the colour bands white, white, orange. What is its value in kilo-ohms (kΩ)? =
  39. 39.🔺 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
  40. 40.🔺 A 1 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =

Answer key

  1. 1
  2. 1.5
  3. 7.5
  4. 78
  5. switch off empty rooms
  6. 377
  7. 15
  8. 24
  9. 160
  10. P = V × I
  11. 30
  12. 920
  13. 7
  14. 0.25
  15. 0.2
  16. iron one shirt at a time
  17. True
  18. 0.3
  19. 0.2
  20. energy used each second
  21. 6
  22. the one nearest an end
  23. an LED lamp
  24. 10
  25. 8
  26. 4.8
  27. 23.5
  28. 7.5
  29. True
  30. V = I × R
  31. 6
  32. 1.25
  33. grey-black-orange
  34. anode (+)
  35. to limit the current
  36. 3
  37. 0.2
  38. 99
  39. I = V ÷ R
  40. 0.2

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