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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 533 · 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 water-pipe picture of a circuit, current is like … (a) the pipe colour (b) the flow of water (c) a narrow pipe (d) the water pressure
  2. 2.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
  3. 3.🧾 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?
  4. 4.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  5. 5.🔺 A current of 40 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  6. 6.🧩 Which component glows using little power? (a) resistor (b) LED (c) thermistor (d) buzzer
  7. 7.🔺 A 3 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  8. 8.🔺 A current of 1 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  9. 9.Which of these saves electricity? (a) use old filament bulbs (b) run fans in empty rooms (c) leave fridge door open (d) close the fridge quickly
  10. 10.What does a buzzer do? (a) turns a fan or wheels (b) boosts a small signal (c) is a resistance knob (d) makes a beeping sound
  11. 11.📏 How many kilowatts (kW) is 450 W? =
  12. 12.🔺 A 1.2 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  13. 13.🌈 A resistor has the colour bands white, green, red. What is its value (in ohms)?
  14. 14.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  15. 15.📏 How many watts (W) is 3.9 kW?
  16. 16.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) less than either one (d) more than either one
  17. 17.🧩 Which component makes things spin? (a) LDR (b) motor (c) buzzer (d) potentiometer
  18. 18.🔺 A current of 2.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it does not light (d) it changes colour
  20. 20.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  22. 22.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = V ÷ I (d) P = I ÷ V
  23. 23.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  24. 24.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = R ÷ I (c) V = I + R (d) V = I ÷ R
  25. 25.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 0 % (d) 25 %
  26. 26.📏 How many kilo-ohms (kΩ) is 8100 Ω? =
  27. 27.📏 Voltmeter or ammeter: which one is joined in series? (a) ammeter (b) voltmeter
  28. 28.🔺 A current of 1.5 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  29. 29.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  30. 30.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  31. 31.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  32. 32.True or false: a buzzer makes a beeping sound. (a) True (b) False
  33. 33.🔺 A 16.5 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
  34. 34.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
  35. 35.💡 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?
  36. 36.🌈 In the resistor colour code, which number does red stand for?
  37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 41 Ω resistor? (a) green-brown-black (b) yellow-brown-black (c) brown-yellow-black (d) yellow-brown-brown
  38. 38.🧮 Resistors of 50 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
  39. 39.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  40. 40.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

Answer key

  1. the flow of water
  2. 5
  3. 204
  4. 1
  5. 100
  6. LED
  7. 25
  8. 4
  9. close the fridge quickly
  10. makes a beeping sound
  11. 0.45
  12. 10
  13. 9500
  14. 115
  15. 3900
  16. less than either one
  17. motor
  18. 50
  19. it does not light
  20. 18.8
  21. 9.4
  22. P = V × I
  23. 500
  24. V = I × R
  25. 5 %
  26. 8.1
  27. ammeter
  28. 2
  29. 1
  30. cathode (−)
  31. 300
  32. True
  33. 50
  34. ammeter
  35. 360
  36. 2
  37. yellow-brown-black
  38. 70
  39. 5
  40. 50

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