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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 132 · 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.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  2. 2.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  3. 3.🧩 Which component turns a fan or wheels? (a) buzzer (b) LED (c) motor (d) LDR
  4. 4.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
  5. 5.True or false: an LED limits the current. (a) False (b) True
  6. 6.🧮 A 2.4 V battery is joined to 8 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
  7. 7.🔺 A current of 50 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
  8. 8.🌈 A resistor has the colour bands white, green, black. What is its value (in ohms)?
  9. 9.📏 How many kilowatts (kW) is 4500 W? =
  10. 10.🧮 A 47 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  11. 11.True or false: the ammeter is joined across a part. (a) False (b) True
  12. 12.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) gets smaller (c) stays the same (d) becomes zero
  13. 13.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 0 % (c) 25 % (d) 5 %
  14. 14.What does a potentiometer do? (a) is a resistance knob (b) smooths a wobbly supply (c) boosts a small signal (d) glows using little power
  15. 15.True or false: a fuse glows using little power. (a) False (b) True
  16. 16.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  17. 17.Which of these wastes electricity? (a) use daylight to read (b) switch off empty rooms (c) unplug idle chargers (d) use old filament bulbs
  18. 18.🌈 In the resistor colour code, which number does green stand for?
  19. 19.🔺 A current of 2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  20. 20.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a buzzer (c) a diode (d) a resistor
  21. 21.🔺 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
  22. 22.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
  23. 23.📏 In the water-pipe picture of a circuit, current is like … (a) the pipe colour (b) a narrow pipe (c) the water pressure (d) the flow of water
  24. 24.🧮 Resistors of 68 Ω, 47 Ω, 150 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
  25. 25.🔺 A 7.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  26. 26.🔺 A 0.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  27. 27.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =
  28. 28.🔺 A current of 0.2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🔺 A 0.2 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  30. 30.🔺 A 5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  31. 31.True or false: a resistor senses how bright it is. (a) True (b) False
  32. 32.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 61 Ω resistor? (a) violet-brown-black (b) blue-brown-brown (c) blue-brown-black (d) brown-blue-black
  33. 33.🧮 Resistors of 33 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
  34. 34.💡 An LED is joined to a 3 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) lights up (b) may burn out (c) does not light
  35. 35.🧮 Resistors of 22 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
  36. 36.💡 What happens if an LED is put in backwards? (a) it does not light (b) it makes a sound (c) it lights brighter (d) it changes colour
  37. 37.🔺 A current of 2 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  38. 38.🧮 A 10 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  39. 39.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
  40. 40.🔺 A current of 3 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. cathode (−)
  2. 15
  3. motor
  4. 3
  5. False
  6. 0.2
  7. 150
  8. 95
  9. 4.5
  10. 157
  11. False
  12. gets smaller
  13. 5 %
  14. is a resistance knob
  15. False
  16. 20
  17. use old filament bulbs
  18. 5
  19. 4
  20. a buzzer
  21. R = V ÷ I
  22. 4.5
  23. the flow of water
  24. 485
  25. 2.5
  26. 0.1
  27. 0.9
  28. 3
  29. 0.1
  30. 0.5
  31. False
  32. blue-brown-black
  33. 133
  34. does not light
  35. 122
  36. it does not light
  37. 24
  38. 20
  39. 2.5
  40. 18

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