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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 385 · 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 20 mA flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
  2. 2.🧮 A 6 V battery is joined to 10 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
  3. 3.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
  4. 4.What does a motor do? (a) lets current go one way (b) is a resistance knob (c) makes things spin (d) boosts a small signal
  5. 5.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 34000 Ω resistor? (a) orange-yellow-orange (b) orange-yellow-red (c) orange-yellow-yellow (d) yellow-orange-orange
  6. 6.⚡ A 13.5 W device works on 9 V. What current does it take (in amperes)? =
  7. 7.🔺 A 12 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
  8. 8.🌈 In the resistor colour code, which number does yellow stand for?
  9. 9.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
  10. 10.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
  11. 11.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  12. 12.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  13. 13.True or false: to switch off empty rooms wastes electricity. (a) False (b) True
  14. 14.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = V × I (d) P = I ÷ V
  15. 15.🌈 In the resistor colour code, which number does green stand for?
  16. 16.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  17. 17.🔺 A 0.75 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  18. 18.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
  19. 19.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a resistor (c) a motor (d) an LED
  20. 20.💡 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)?
  21. 21.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
  22. 22.🧮 Resistors of 20 Ω, 50 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
  23. 23.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1024 (b) 10 (c) 100 (d) 1000
  24. 24.⚡ A device works on 12 V and takes 2 A. What is its power (in watts)? =
  25. 25.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an LED lamp (d) an oil lamp
  26. 26.💡 An LED is joined to a 3 V battery through a 1000 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) does not light (b) may burn out (c) lights up
  27. 27.🔺 A current of 2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  28. 28.⚡ Power tells us … (a) the size of a cell (b) energy used each second (c) the length of a wire (d) the colour of light
  29. 29.Which of these is measured in volts (V)? (a) how much a part resists (b) current (c) the push of a cell (d) the flow of charge
  30. 30.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  31. 31.🧮 A 1.8 V battery is joined to 12 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
  32. 32.🔺 A 0.6 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  33. 33.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to limit the current (d) to store charge
  34. 34.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
  35. 35.⚡ A 36 W device works on 24 V. What current does it take (in amperes)? =
  36. 36.🔺 An 8.8 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
  37. 37.True or false: a motor beeps for an alarm. (a) True (b) False
  38. 38.🌈 A resistor has the colour bands brown, yellow, black. What is its value (in ohms)?
  39. 39.🧾 A 1000 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
  40. 40.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True

Answer key

  1. 100
  2. 0.5
  3. saves electricity
  4. makes things spin
  5. orange-yellow-orange
  6. 1.5
  7. 40
  8. 4
  9. 2300
  10. V = I × R
  11. cathode (−)
  12. 1840
  13. False
  14. P = V × I
  15. 5
  16. 5
  17. 0.25
  18. False
  19. a motor
  20. 15
  21. 1
  22. 220
  23. 1000
  24. 24
  25. an LED lamp
  26. does not light
  27. 40
  28. energy used each second
  29. the push of a cell
  30. 4
  31. 0.1
  32. 0.2
  33. to limit the current
  34. True
  35. 1.5
  36. 40
  37. False
  38. 14
  39. 5
  40. True

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