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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 490 · 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 V? (a) V = I + R (b) V = I × R (c) V = R ÷ I (d) V = I ÷ R
  2. 2.📏 In the water-pipe picture of a circuit, current is like … (a) the flow of water (b) a narrow pipe (c) the water pressure (d) the pipe colour
  3. 3.💡 An LED is joined to a 6 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) does not light (c) lights up
  4. 4.🔺 A 3 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
  5. 5.🧮 A 50 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)?
  6. 6.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  7. 7.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to change its colour (c) to make it brighter (d) to store charge
  8. 8.💡 Does it save or waste electricity to run fans in empty rooms? (a) wastes electricity (b) saves electricity
  9. 9.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  10. 10.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V ÷ R (c) I = R ÷ V (d) I = V + R
  11. 11.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 20000 Ω resistor? (a) orange-red-orange (b) red-black-orange (c) red-black-red (d) red-black-yellow
  12. 12.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  13. 13.🔺 A current of 2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  14. 14.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
  15. 15.🌈 In the resistor colour code, which number does white stand for?
  16. 16.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🔺 A 2 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  18. 18.🔺 A current of 3 A flows through a 4 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 does not light (c) it changes colour (d) it makes a sound
  20. 20.🌈 A resistor has the colour bands brown, orange, black. What is its value (in ohms)?
  21. 21.⚡ A device works on 3 V and takes 0.25 A. What is its power (in watts)? =
  22. 22.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) stay the same (d) zero
  23. 23.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a motor (d) a fuse
  24. 24.Which of these saves electricity? (a) leave the TV on standby (b) leave fridge door open (c) use LED lamps (d) iron one shirt at a time
  25. 25.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 0 % (d) 5 %
  26. 26.🔺 A current of 10 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  27. 27.⚡ A 72 W device works on 24 V. What current does it take (in amperes)? =
  28. 28.🧾 A 100 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
  29. 29.🔺 A 4 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  30. 30.True or false: to leave the TV on standby wastes electricity. (a) True (b) False
  31. 31.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
  32. 32.🌈 Which band is read first on a resistor? (a) the widest gap (b) the gold band (c) the one nearest an end (d) any band
  33. 33.📏 Which unit measures energy used each second? (a) ampere (A) (b) ohm (Ω) (c) volt (V) (d) watt (W)
  34. 34.True or false: a transistor boosts a small signal. (a) True (b) False
  35. 35.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  36. 36.📏 Which unit measures how much a part resists? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
  37. 37.True or false: to switch off empty rooms saves electricity. (a) False (b) True
  38. 38.🔺 An 18 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
  39. 39.🔺 A current of 3 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) less than either one (d) their sum

Answer key

  1. V = I × R
  2. the flow of water
  3. may burn out
  4. 10
  5. 70
  6. cathode (−)
  7. to limit the current
  8. wastes electricity
  9. 345
  10. I = V ÷ R
  11. red-black-orange
  12. 100
  13. 2
  14. 6
  15. 9
  16. 2
  17. 20
  18. 12
  19. it does not light
  20. 13
  21. 0.75
  22. bigger
  23. a motor
  24. use LED lamps
  25. 5 %
  26. 2.2
  27. 3
  28. 0.5
  29. 2
  30. True
  31. ammeter
  32. the one nearest an end
  33. watt (W)
  34. True
  35. 160
  36. ohm (Ω)
  37. True
  38. 3
  39. 45
  40. less than either one

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