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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 690 · 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.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V + R (c) I = V × R (d) I = R ÷ V
  2. 2.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  3. 3.🌈 A resistor has the colour bands orange, brown, yellow. What is its value in kilo-ohms (kΩ)? =
  4. 4.🧩 Which component makes things spin? (a) diode (b) motor (c) buzzer (d) resistor
  5. 5.🌈 A resistor has the colour bands violet, violet, yellow. What is its value in kilo-ohms (kΩ)? =
  6. 6.🔺 A current of 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.🧾 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?
  8. 8.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) an LED (d) a fuse
  9. 9.🔺 A current of 2 A flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
  10. 10.True or false: to leave the TV on standby wastes electricity. (a) True (b) False
  11. 11.🧮 Two resistors in parallel give a total that is … (a) always zero (b) more than either one (c) less than either one (d) their sum
  12. 12.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  13. 13.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) gets bigger (d) stays the same
  14. 14.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 10 (b) 1000 (c) 100 (d) 1024
  15. 15.🔺 A current of 2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  16. 16.🌈 A resistor has the colour bands violet, brown, black. What is its value (in ohms)?
  17. 17.🔺 A current of 1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  18. 18.⚡ A 0.3 W device works on 3 V. What current does it take (in amperes)? =
  19. 19.Which of these saves electricity? (a) use old filament bulbs (b) leave the TV on standby (c) use LED lamps (d) run fans in empty rooms
  20. 20.💡 An LED is joined to a 12 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) lights up (c) may burn out
  21. 21.🔺 A current of 0.25 A flows when 0.5 V is joined across a resistor. What is its resistance (in ohms)?
  22. 22.🔺 A current of 40 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  23. 23.🧮 A 22 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)?
  24. 24.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  25. 25.🔍 Which is the odd one out? (a) leave the TV on standby (b) switch off empty rooms (c) iron one shirt at a time (d) run fans in empty rooms
  26. 26.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it lights brighter (c) it does not light (d) it makes a sound
  27. 27.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 10 (c) 1000 (d) 100
  28. 28.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 5 V supply. What current flows (in mA)?
  29. 29.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an oil lamp (d) an LED lamp
  30. 30.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
  31. 31.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to change its colour (d) to limit the current
  32. 32.True or false: a capacitor smooths a wobbly supply. (a) False (b) True
  33. 33.🌈 A resistor has the colour bands blue, orange, black. What is its value (in ohms)?
  34. 34.True or false: a fuse is a resistance knob. (a) True (b) False
  35. 35.🔺 A current of 0.2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.🧮 Resistors of 68 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
  37. 37.🔺 An 8.25 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
  38. 38.📏 Voltmeter or ammeter: which one is joined in series? (a) ammeter (b) voltmeter
  39. 39.⚡ An 18 W device works on 12 V. What current does it take (in amperes)? =
  40. 40.🧾 A 1500 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =

Answer key

  1. I = V ÷ R
  2. 10
  3. 310
  4. motor
  5. 770
  6. 6
  7. 189
  8. a motor
  9. 4
  10. True
  11. less than either one
  12. 165
  13. gets smaller
  14. 1000
  15. 30
  16. 71
  17. 6
  18. 0.1
  19. use LED lamps
  20. may burn out
  21. 2
  22. 250
  23. 42
  24. anode (+)
  25. switch off empty rooms
  26. it does not light
  27. 1000
  28. 15
  29. an LED lamp
  30. bigger
  31. to limit the current
  32. True
  33. 63
  34. False
  35. 1
  36. 538
  37. 25
  38. ammeter
  39. 1.5
  40. 3

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