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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 564 · 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.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to make it brighter (c) to store charge (d) to change its colour
  2. 2.What does a potentiometer do? (a) stores a little charge (b) smooths a wobbly supply (c) limits the current (d) is a resistance knob
  3. 3.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
  4. 4.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  5. 5.🔺 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
  6. 6.🔺 A 0.75 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  7. 7.📏 How many ohms (Ω) is 5.5 kΩ?
  8. 8.🧩 Which part changes electrical energy into movement? (a) a fuse (b) an LED (c) a motor (d) a resistor
  9. 9.🔺 An 18.8 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  10. 10.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  11. 11.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = R ÷ V (c) I = V ÷ R (d) I = V × R
  12. 12.🔺 A current of 2 A flows when 24 V is joined across a resistor. What is its resistance (in ohms)?
  13. 13.🔍 Which is the odd one out? (a) close the fridge quickly (b) unplug idle chargers (c) iron one shirt at a time (d) use daylight to read
  14. 14.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 50000 Ω resistor? (a) blue-green-orange (b) green-black-yellow (c) green-black-red (d) green-black-orange
  15. 15.🧾 A 250 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
  16. 16.Which of these wastes electricity? (a) set the AC to 24 °C (b) switch off empty rooms (c) use LED lamps (d) run fans in empty rooms
  17. 17.True or false: a fuse has coloured bands. (a) False (b) True
  18. 18.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) stay the same (c) zero (d) smaller
  19. 19.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  20. 20.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 25 % (d) 0 %
  21. 21.🌈 Which band is read first on a resistor? (a) the widest gap (b) the gold band (c) the one nearest an end (d) any band
  22. 22.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
  23. 23.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  24. 24.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  25. 25.Which of these is measured in amperes (A)? (a) resistance (b) energy used each second (c) the flow of charge (d) voltage
  26. 26.🧮 Resistors of 100 Ω, 47 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
  27. 27.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  28. 28.📏 How many amperes (A) is 1240 mA? =
  29. 29.📏 Which unit measures resistance? (a) ohm (Ω) (b) watt (W) (c) volt (V) (d) ampere (A)
  30. 30.📏 Which unit measures the flow of charge? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
  31. 31.🧾 A 50 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
  32. 32.🔺 A current of 40 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  33. 33.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets bigger (d) gets smaller
  34. 34.🔺 A current of 25 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.🔺 A 5 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  36. 36.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  37. 37.🔺 A current of 1.5 A flows when 9 V is joined across a resistor. What is its resistance (in ohms)?
  38. 38.💡 Does it save or waste electricity to unplug idle chargers? (a) saves electricity (b) wastes electricity
  39. 39.True or false: a motor senses how bright it is. (a) True (b) False
  40. 40.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a diode (c) a buzzer (d) a resistor

Answer key

  1. to limit the current
  2. is a resistance knob
  3. True
  4. 10
  5. V = I × R
  6. 0.25
  7. 5500
  8. a motor
  9. 40
  10. 10
  11. I = V ÷ R
  12. 12
  13. iron one shirt at a time
  14. green-black-orange
  15. 1.25
  16. run fans in empty rooms
  17. False
  18. bigger
  19. cathode (−)
  20. 5 %
  21. the one nearest an end
  22. 189
  23. 10
  24. 5
  25. the flow of charge
  26. 169
  27. 100
  28. 1.24
  29. ohm (Ω)
  30. ampere (A)
  31. 0.1
  32. 100
  33. gets smaller
  34. 2.5
  35. 0.25
  36. 25
  37. 6
  38. saves electricity
  39. False
  40. a buzzer

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