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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 241 · 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.

NameDateTime takenScore ___ / 40
  1. 1.True or false: a transistor makes a beeping sound. (a) False (b) True
  2. 2.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
  3. 3.What does a potentiometer do? (a) is a resistance knob (b) blows if current is high (c) limits the current (d) smooths a wobbly supply
  4. 4.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  5. 5.🧮 Five equal 500 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  6. 6.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
  7. 7.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  8. 8.🧮 Resistors of 330 Ω, 220 Ω, 47 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
  9. 9.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to limit the current (d) to change its colour
  11. 11.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity
  12. 12.🔺 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
  13. 13.True or false: the ammeter measures voltage. (a) False (b) True
  14. 14.⚡ A 4.5 W device works on 3 V. What current does it take (in amperes)? =
  15. 15.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
  16. 16.💡 A red LED uses 2 V and should get 10 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  17. 17.🧩 Which part changes electrical energy into movement? (a) an LED (b) a fuse (c) a resistor (d) a motor
  18. 18.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.What does a thermistor do? (a) makes things spin (b) boosts a small signal (c) makes a beeping sound (d) senses how hot it is
  20. 20.⚡ Which formula gives electric power? (a) P = V × I (b) P = I ÷ V (c) P = V ÷ I (d) P = V + I
  21. 21.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  22. 22.🔺 A current of 40 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  23. 23.📏 How many ohms (Ω) is 6.1 kΩ?
  24. 24.🌈 A resistor has the colour bands white, grey, orange. What is its value in kilo-ohms (kΩ)? =
  25. 25.🌈 In the resistor colour code, which number does green stand for?
  26. 26.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  27. 27.Which of these saves electricity? (a) unplug idle chargers (b) iron one shirt at a time (c) run fans in empty rooms (d) leave fridge door open
  28. 28.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🔺 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
  30. 30.True or false: power is measured in watts (W). (a) False (b) True
  31. 31.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
  32. 32.🔺 A current of 0.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 1400 Ω resistor? (a) brown-yellow-red (b) brown-yellow-orange (c) brown-yellow-brown (d) yellow-brown-red
  34. 34.🔺 A 3.3 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
  35. 35.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 watt (c) 1 kilowatt-hour (kWh) (d) 1 ampere
  36. 36.🧾 A 1000 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
  37. 37.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
  38. 38.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  39. 39.📏 Which unit measures the push of a cell? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
  40. 40.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. False
  2. voltmeter
  3. is a resistance knob
  4. 4
  5. 100
  6. True
  7. 5
  8. 607
  9. 23.5
  10. to limit the current
  11. wastes electricity
  12. gets smaller
  13. False
  14. 1.5
  15. 5 %
  16. 400
  17. a motor
  18. 1
  19. senses how hot it is
  20. P = V × I
  21. 100
  22. 13.2
  23. 6100
  24. 98
  25. 5
  26. 0.5
  27. unplug idle chargers
  28. 6
  29. I = V ÷ R
  30. True
  31. 120
  32. 2.5
  33. brown-yellow-red
  34. 10
  35. 1 kilowatt-hour (kWh)
  36. 2
  37. 595
  38. 2.4
  39. volt (V)
  40. 1.2

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