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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 245 · 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.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  2. 2.💡 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?
  3. 3.🧾 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?
  4. 4.🧮 Three equal 75 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  5. 5.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  6. 6.Which of these saves electricity? (a) iron one shirt at a time (b) leave fridge door open (c) leave the TV on standby (d) use LED lamps
  7. 7.🔺 An 8.25 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
  8. 8.🔺 A current of 2 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  9. 9.🔺 A current of 25 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.🌈 A resistor has the colour bands white, white, red. What is its value in kilo-ohms (kΩ)? =
  12. 12.🔺 A current of 2 A flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
  13. 13.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
  14. 14.🔍 Which is the odd one out? (a) use daylight to read (b) use LED lamps (c) close the fridge quickly (d) use old filament bulbs
  15. 15.📏 How many kilowatts (kW) is 4950 W? =
  16. 16.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 0 % (d) 25 %
  17. 17.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
  18. 18.🔺 A current of 2.5 A flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  19. 19.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a capacitor (d) a buzzer
  20. 20.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) bigger (d) zero
  21. 21.🌈 A resistor has the colour bands green, black, black. What is its value (in ohms)?
  22. 22.💡 Does it save or waste electricity to iron one shirt at a time? (a) saves electricity (b) wastes electricity
  23. 23.🧩 Which component makes things spin? (a) fuse (b) motor (c) buzzer (d) potentiometer
  24. 24.📏 In the water-pipe picture of a circuit, current is like … (a) a narrow pipe (b) the water pressure (c) the pipe colour (d) the flow of water
  25. 25.🔺 A 5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
  26. 26.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  27. 27.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
  28. 28.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
  29. 29.🧮 Resistors of 330 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
  30. 30.📏 How many amperes (A) is 380 mA? =
  31. 31.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
  32. 32.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.🔺 A current of 50 mA flows when 16.5 V is joined across a resistor. What is its resistance (in ohms)?
  34. 34.🌈 A resistor has the colour bands blue, green, black. What is its value (in ohms)?
  35. 35.📏 Which unit measures the push of a cell? (a) ampere (A) (b) ohm (Ω) (c) volt (V) (d) watt (W)
  36. 36.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V × I (c) R = I ÷ V (d) R = V ÷ I
  37. 37.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  38. 38.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  39. 39.⚡ A 1.2 W device works on 12 V. What current does it take (in amperes)? =
  40. 40.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity

Answer key

  1. 25
  2. 160
  3. 85
  4. 25
  5. 1
  6. use LED lamps
  7. 25
  8. 3
  9. 2.5
  10. 2.4
  11. 9.9
  12. 4
  13. 330
  14. use old filament bulbs
  15. 4.95
  16. 5 %
  17. 460
  18. 4
  19. a buzzer
  20. bigger
  21. 50
  22. wastes electricity
  23. motor
  24. the flow of water
  25. 10
  26. 5
  27. energy used each second
  28. 510
  29. 398
  30. 0.38
  31. 0.25
  32. 11.75
  33. 330
  34. 65
  35. volt (V)
  36. R = V ÷ I
  37. 5.5
  38. cathode (−)
  39. 0.1
  40. saves electricity

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