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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 547 · 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.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a motor (d) a fuse
  2. 2.⚡ A device works on 5 V and takes 3 A. What is its power (in watts)? =
  3. 3.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) less than either one (d) always zero
  4. 4.⚡ Which formula gives electric power? (a) P = V × I (b) P = I ÷ V (c) P = V + I (d) P = V ÷ I
  5. 5.True or false: the push of a cell is measured in ohms (Ω). (a) True (b) False
  6. 6.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
  7. 7.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  8. 8.What does a potentiometer do? (a) limits the current (b) beeps for an alarm (c) is a resistance knob (d) boosts a small signal
  9. 9.🔺 A 25 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  10. 10.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.🔺 A current of 50 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.🔺 A 16 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  13. 13.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.🧮 Resistors of 470 Ω, 47 Ω, 33 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
  15. 15.🔺 An 18.8 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  16. 16.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  17. 17.⚡ A 1.2 W device works on 12 V. What current does it take (in amperes)? =
  18. 18.🌈 A resistor has the colour bands brown, blue, brown. What is its value (in ohms)?
  19. 19.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to make it brighter (c) to change its colour (d) to store charge
  20. 20.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🔍 Which is the odd one out? (a) leave the TV on standby (b) use old filament bulbs (c) iron one shirt at a time (d) unplug idle chargers
  22. 22.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
  23. 23.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it changes colour (c) it does not light (d) it lights brighter
  24. 24.🔺 A 0.75 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  25. 25.🌈 In the resistor colour code, which number does brown stand for?
  26. 26.🔺 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
  27. 27.Which of these is measured in amperes (A)? (a) energy used each second (b) how much a part resists (c) current (d) the push of a cell
  28. 28.🌈 Which band is read first on a resistor? (a) any band (b) the widest gap (c) the one nearest an end (d) the gold band
  29. 29.🔺 A current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  30. 30.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 25 % (c) 50 % (d) 5 %
  31. 31.🧮 Resistors of 47 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
  32. 32.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  33. 33.📏 Which unit measures power? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
  34. 34.💡 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?
  35. 35.🔺 A 15 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  36. 36.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 1500 Ω resistor? (a) brown-green-red (b) brown-green-orange (c) brown-green-brown (d) green-brown-red
  37. 37.🔺 A current of 1 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  38. 38.🔺 A current of 40 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  39. 39.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?

Answer key

  1. a motor
  2. 15
  3. less than either one
  4. P = V × I
  5. False
  6. voltmeter
  7. anode (+)
  8. is a resistance knob
  9. 2.5
  10. 4
  11. 120
  12. 2
  13. 5
  14. 770
  15. 40
  16. 115
  17. 0.1
  18. 160
  19. to limit the current
  20. 3
  21. unplug idle chargers
  22. True
  23. it does not light
  24. 0.25
  25. 1
  26. I = V ÷ R
  27. current
  28. the one nearest an end
  29. 5
  30. 5 %
  31. 67
  32. cathode (−)
  33. watt (W)
  34. 360
  35. 1
  36. brown-green-red
  37. 15
  38. 8.8
  39. 37.5
  40. 567

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