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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 440 · 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 blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  2. 2.🔺 A 4 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  3. 3.🌈 Which band is read first on a resistor? (a) the gold band (b) any band (c) the widest gap (d) the one nearest an end
  4. 4.⚡ Power tells us … (a) energy used each second (b) the length of a wire (c) the size of a cell (d) the colour of light
  5. 5.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 5 V supply. What current flows (in mA)?
  6. 6.🧮 A 150 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  7. 7.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
  8. 8.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
  9. 9.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
  10. 10.📏 How many milliamperes (mA) is 0.03 A?
  11. 11.True or false: the voltmeter is joined across a part. (a) False (b) True
  12. 12.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 25 % (d) 50 %
  13. 13.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.True or false: a motor makes a beeping sound. (a) True (b) False
  15. 15.🌈 A resistor has the colour bands orange, orange, black. What is its value (in ohms)?
  16. 16.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  17. 17.🧮 Resistors of 20 Ω, 330 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
  18. 18.🔺 A current of 3 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
  20. 20.🔺 A 6 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
  21. 21.🔺 A 20 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  22. 22.🔍 Which is the odd one out? (a) close the fridge quickly (b) switch off empty rooms (c) use LED lamps (d) use old filament bulbs
  23. 23.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
  24. 24.🔺 A 2 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
  25. 25.Which of these wastes electricity? (a) unplug idle chargers (b) close the fridge quickly (c) switch off empty rooms (d) iron one shirt at a time
  26. 26.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) stays the same (d) gets bigger
  27. 27.🧮 A 470 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  28. 28.🔺 A current of 0.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a capacitor (c) a diode (d) a resistor
  30. 30.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
  31. 31.Which of these saves electricity? (a) leave the TV on standby (b) use old filament bulbs (c) use LED lamps (d) iron one shirt at a time
  32. 32.What does a thermistor do? (a) senses how hot it is (b) blows if current is high (c) turns a fan or wheels (d) stores a little charge
  33. 33.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
  34. 34.📏 Which unit measures voltage? (a) ampere (A) (b) watt (W) (c) volt (V) (d) ohm (Ω)
  35. 35.🌈 In the resistor colour code, which number does green stand for?
  36. 36.💡 What does LED stand for? (a) large electric dial (b) light energy dial (c) low energy device (d) light-emitting diode
  37. 37.⚡ A device works on 6 V and takes 0.2 A. What is its power (in watts)? =
  38. 38.💡 Does it save or waste electricity to close the fridge quickly? (a) saves electricity (b) wastes electricity
  39. 39.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.📏 How many kilowatts (kW) is 1050 W? =

Answer key

  1. 360
  2. 0.2
  3. the one nearest an end
  4. energy used each second
  5. 10
  6. 170
  7. 255
  8. 10
  9. 120
  10. 30
  11. True
  12. 5 %
  13. 3
  14. False
  15. 33
  16. 150
  17. 400
  18. 36
  19. 850
  20. 40
  21. 1
  22. use old filament bulbs
  23. V = I × R
  24. 10
  25. iron one shirt at a time
  26. gets smaller
  27. 970
  28. 7.5
  29. a buzzer
  30. 315
  31. use LED lamps
  32. senses how hot it is
  33. voltmeter
  34. volt (V)
  35. 5
  36. light-emitting diode
  37. 1.2
  38. saves electricity
  39. 2
  40. 1.05

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