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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 980 · 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 48 W device works on 24 V. What current does it take (in amperes)? =
  2. 2.True or false: a capacitor smooths a wobbly supply. (a) False (b) True
  3. 3.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = V ÷ I (d) P = I ÷ V
  4. 4.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = V ÷ R (d) I = R ÷ V
  5. 5.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
  6. 6.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) the gold band (d) any band
  7. 7.🌈 In the resistor colour code, which number does blue stand for?
  8. 8.💡 What happens if an LED is put in backwards? (a) it does not light (b) it changes colour (c) it makes a sound (d) it lights brighter
  9. 9.📏 In the water-pipe picture of a circuit, current is like … (a) the pipe colour (b) the water pressure (c) a narrow pipe (d) the flow of water
  10. 10.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
  11. 11.🔺 A current of 10 mA flows when 4.7 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  13. 13.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 watt (d) 1 ampere
  14. 14.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
  15. 15.⚡ A device works on 1.5 V and takes 0.2 A. What is its power (in watts)? =
  16. 16.Which of these wastes electricity? (a) use old filament bulbs (b) close the fridge quickly (c) use LED lamps (d) switch off empty rooms
  17. 17.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  18. 18.True or false: a buzzer makes a beeping sound. (a) False (b) True
  19. 19.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) does not light (c) lights up
  20. 20.🔺 A current of 0.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🔺 A current of 50 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  22. 22.🔺 A current of 0.5 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  23. 23.🔺 A 7.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
  24. 24.True or false: current is measured in volts (V). (a) True (b) False
  25. 25.💡 Does it save or waste electricity to run fans in empty rooms? (a) wastes electricity (b) saves electricity
  26. 26.📏 How many ohms (Ω) is 9.8 kΩ?
  27. 27.True or false: a thermistor senses how bright it is. (a) False (b) True
  28. 28.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
  29. 29.🔺 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
  30. 30.🔺 A current of 2 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  31. 31.🔺 A 23.5 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  32. 32.🔺 A current of 0.25 A flows when 0.5 V is joined across a resistor. What is its resistance (in ohms)?
  33. 33.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  34. 34.📏 How many kilo-ohms (kΩ) is 3600 Ω? =
  35. 35.🔺 A current of 2.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.True or false: the voltmeter measures voltage. (a) False (b) True
  37. 37.🔺 A 3 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  38. 38.📏 Which unit measures how much a part resists? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
  39. 39.🧮 Resistors of 10 Ω, 47 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
  40. 40.🔺 A current of 10 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. 2
  2. True
  3. P = V × I
  4. I = V ÷ R
  5. ammeter
  6. the one nearest an end
  7. 6
  8. it does not light
  9. the flow of water
  10. False
  11. 470
  12. 230
  13. 1 kilowatt-hour (kWh)
  14. 510
  15. 0.3
  16. use old filament bulbs
  17. 18.8
  18. True
  19. lights up
  20. 2
  21. 120
  22. 6
  23. 50
  24. False
  25. wastes electricity
  26. 9800
  27. False
  28. 20
  29. V = I × R
  30. 10
  31. 50
  32. 2
  33. 10
  34. 3.6
  35. 5
  36. True
  37. 0.2
  38. ohm (Ω)
  39. 527
  40. 4.7

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