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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 650 · 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 12 W device works on 6 V. What current does it take (in amperes)? =
  2. 2.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  3. 3.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 7700 Ω resistor? (a) violet-violet-brown (b) violet-violet-orange (c) violet-violet-red (d) violet-grey-red
  4. 4.🔺 A current of 25 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  5. 5.💡 A red LED uses 2 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  6. 6.True or false: a potentiometer is a resistance knob. (a) False (b) True
  7. 7.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
  8. 8.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.🔺 A current of 0.2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
  11. 11.🌈 A resistor has the colour bands yellow, blue, orange. What is its value (in ohms)?
  12. 12.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a buzzer (c) a capacitor (d) a diode
  13. 13.📏 How many watts (W) is 4.6 kW?
  14. 14.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
  15. 15.🧮 A 1.2 V battery is joined to 8 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
  16. 16.📏 How many watts (W) is 3.5 kW?
  17. 17.🌈 A resistor has the colour bands brown, violet, brown. What is its value (in ohms)?
  18. 18.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  20. 20.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
  21. 21.🌈 A resistor has the colour bands brown, white, yellow. What is its value in kilo-ohms (kΩ)? =
  22. 22.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 25 % (c) 50 % (d) 0 %
  23. 23.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 49000 Ω resistor? (a) yellow-white-yellow (b) white-yellow-orange (c) yellow-white-orange (d) yellow-white-red
  24. 24.🔺 A current of 25 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
  25. 25.🔺 A current of 1 A flows when 12 V is joined across a resistor. What is its resistance (in ohms)?
  26. 26.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 75000 Ω resistor? (a) green-violet-orange (b) violet-green-red (c) violet-green-yellow (d) violet-green-orange
  27. 27.🧮 A 100 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  28. 28.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V × I (d) P = V + I
  29. 29.What does a motor do? (a) turns a fan or wheels (b) is a resistance knob (c) smooths a wobbly supply (d) boosts a small signal
  30. 30.🔍 Which is the odd one out? (a) leave the TV on standby (b) leave fridge door open (c) set the AC to 24 °C (d) run fans in empty rooms
  31. 31.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
  32. 32.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to store charge (d) to limit the current
  33. 33.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  34. 34.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 100 (c) 10 (d) 1000
  35. 35.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) stay the same (d) zero
  36. 36.Which of these is measured in ohms (Ω)? (a) how much a part resists (b) power (c) current (d) energy used each second
  37. 37.True or false: the ammeter measures voltage. (a) True (b) False
  38. 38.True or false: the voltmeter is joined in series. (a) True (b) False
  39. 39.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = I ÷ V (c) R = V + I (d) R = V ÷ I
  40. 40.📏 Which unit measures resistance? (a) ampere (A) (b) watt (W) (c) volt (V) (d) ohm (Ω)

Answer key

  1. 2
  2. 7.5
  3. violet-violet-red
  4. 120
  5. 350
  6. True
  7. wastes electricity
  8. 0.8
  9. 0.6
  10. 3
  11. 46000
  12. a buzzer
  13. 4600
  14. 204
  15. 0.1
  16. 3500
  17. 170
  18. 12.5
  19. 37.5
  20. 0.2
  21. 190
  22. 5 %
  23. yellow-white-orange
  24. 7.5
  25. 12
  26. violet-green-orange
  27. 150
  28. P = V × I
  29. turns a fan or wheels
  30. set the AC to 24 °C
  31. 4.5
  32. to limit the current
  33. cathode (−)
  34. 1000
  35. bigger
  36. how much a part resists
  37. False
  38. False
  39. R = V ÷ I
  40. ohm (Ω)

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