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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 337 · 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 current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  2. 2.🧩 Which component lets current go one way? (a) motor (b) buzzer (c) resistor (d) diode
  3. 3.🔺 A 7.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  4. 4.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  5. 5.🔺 A 2 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  6. 6.💡 An LED is joined to a 5 V battery through a 220 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
  7. 7.🌈 In the resistor colour code, which number does brown stand for?
  8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4100 Ω resistor? (a) brown-yellow-red (b) yellow-brown-orange (c) yellow-brown-red (d) yellow-brown-brown
  9. 9.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = I ÷ V (d) R = V ÷ I
  11. 11.🧩 Which component makes a beeping sound? (a) motor (b) diode (c) LDR (d) buzzer
  12. 12.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  13. 13.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
  14. 14.🔺 A current of 0.2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  15. 15.🧮 Resistors of 22 Ω, 150 Ω, 100 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
  16. 16.🔺 A 15 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  17. 17.🔺 A current of 0.2 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.⚡ Which formula gives electric power? (a) P = V × I (b) P = V + I (c) P = V ÷ I (d) P = I ÷ V
  19. 19.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
  20. 20.🔺 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
  21. 21.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 5000 Ω resistor? (a) green-black-brown (b) green-black-red (c) blue-green-red (d) green-black-orange
  22. 22.📏 Which unit measures the flow of charge? (a) watt (W) (b) ohm (Ω) (c) ampere (A) (d) volt (V)
  23. 23.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 620 Ω resistor? (a) blue-red-red (b) red-blue-brown (c) blue-red-black (d) blue-red-brown
  24. 24.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
  25. 25.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  26. 26.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) smaller (d) stay the same
  27. 27.What does a buzzer do? (a) makes a beeping sound (b) makes things spin (c) blows if current is high (d) smooths a wobbly supply
  28. 28.💡 What does LED stand for? (a) low energy device (b) light-emitting diode (c) large electric dial (d) light energy dial
  29. 29.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) less than either one (c) always zero (d) their sum
  30. 30.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  31. 31.💡 Does it save or waste electricity to use LED lamps? (a) saves electricity (b) wastes electricity
  32. 32.🔺 A current of 2.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.🧩 Which component senses how bright it is? (a) capacitor (b) fuse (c) LDR (d) resistor
  34. 34.🧾 Which lamp gives the same light for the least power? (a) a candle (b) a filament bulb (c) an LED lamp (d) an oil lamp
  35. 35.🔺 A current of 2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  36. 36.What does a motor do? (a) boosts a small signal (b) senses how hot it is (c) has coloured bands (d) makes things spin
  37. 37.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the colour of light (d) the size of a cell
  38. 38.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  39. 39.🔺 A current of 2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?

Answer key

  1. 5
  2. diode
  3. 2.5
  4. 115
  5. 0.25
  6. lights up
  7. 1
  8. yellow-brown-red
  9. 3.75
  10. R = V ÷ I
  11. buzzer
  12. 450
  13. saves electricity
  14. 4
  15. 292
  16. 1
  17. 15
  18. P = V × I
  19. True
  20. V = I × R
  21. green-black-red
  22. ampere (A)
  23. blue-red-brown
  24. False
  25. 11.75
  26. bigger
  27. makes a beeping sound
  28. light-emitting diode
  29. less than either one
  30. 120
  31. saves electricity
  32. 12.5
  33. LDR
  34. an LED lamp
  35. 2
  36. makes things spin
  37. energy used each second
  38. anode (+)
  39. 10
  40. 102

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