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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 729 · 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.True or false: a capacitor stores a little charge. (a) False (b) True
  2. 2.⚡ A device works on 6 V and takes 0.2 A. What is its power (in watts)? =
  3. 3.🔺 A current of 2.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.📏 In the water-pipe picture of a circuit, current is like … (a) the pipe colour (b) the flow of water (c) the water pressure (d) a narrow pipe
  5. 5.🔺 A current of 3 A flows when 18 V is joined across a resistor. What is its resistance (in ohms)?
  6. 6.🌈 A resistor has the colour bands red, orange, black. What is its value (in ohms)?
  7. 7.🔺 A current of 0.1 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.True or false: the ammeter measures current. (a) False (b) True
  9. 9.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
  10. 10.🔺 A current of 3 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.🧩 Which component turns a fan or wheels? (a) motor (b) resistor (c) fuse (d) LED
  12. 12.🧩 Which component senses how hot it is? (a) LED (b) fuse (c) capacitor (d) thermistor
  13. 13.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
  14. 14.⚡ A 24 W device works on 24 V. What current does it take (in amperes)? =
  15. 15.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = I ÷ V (d) P = V ÷ I
  16. 16.📏 Which unit measures current? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
  17. 17.True or false: an LED glows using little power. (a) True (b) False
  18. 18.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) measure heat (d) store charge briefly
  19. 19.🔺 A 1.25 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  20. 20.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
  21. 21.🔺 A current of 10 mA flows when 1.5 V is joined across a resistor. What is its resistance (in ohms)?
  22. 22.⚡ A 0.3 W device works on 3 V. What current does it take (in amperes)? =
  23. 23.🧮 Resistors of 20 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
  24. 24.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a buzzer (d) a capacitor
  25. 25.🔺 A 30 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  26. 26.🔺 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
  27. 27.💡 A red LED uses 2 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  28. 28.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) a narrow pipe (c) a bigger tank (d) the flow of water
  29. 29.🔍 Which is the odd one out? (a) use LED lamps (b) set the AC to 24 °C (c) leave fridge door open (d) close the fridge quickly
  30. 30.True or false: the ammeter measures voltage. (a) False (b) True
  31. 31.Which of these is measured in amperes (A)? (a) energy used each second (b) the push of a cell (c) the flow of charge (d) how much a part resists
  32. 32.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.🧮 Resistors of 22 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
  34. 34.💡 An LED is joined to a 9 V battery through a 220 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) lights up (c) may burn out
  35. 35.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
  36. 36.🧩 Which component boosts a small signal? (a) resistor (b) motor (c) transistor (d) buzzer
  37. 37.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) the colour of light (d) energy used each second
  38. 38.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
  39. 39.🧮 A 9 V battery is joined to 6 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
  40. 40.🔺 A current of 3 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. True
  2. 1.2
  3. 12.5
  4. the flow of water
  5. 6
  6. 23
  7. 2
  8. True
  9. wastes electricity
  10. 6
  11. motor
  12. thermistor
  13. True
  14. 1
  15. P = V × I
  16. ampere (A)
  17. True
  18. store charge briefly
  19. 0.25
  20. False
  21. 150
  22. 0.1
  23. 240
  24. a buzzer
  25. 2
  26. I = V ÷ R
  27. 350
  28. a narrow pipe
  29. leave fridge door open
  30. False
  31. the flow of charge
  32. 11.75
  33. 55
  34. lights up
  35. 4.5
  36. transistor
  37. energy used each second
  38. 630
  39. 1
  40. 36

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