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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 489 · 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.🧮 Resistors of 47 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
  2. 2.🔺 A current of 50 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  3. 3.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = V + I (d) R = I ÷ V
  4. 4.🔺 A current of 1.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
  5. 5.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 4 hours. How many watt-hours (Wh) are saved?
  6. 6.🌈 In the resistor colour code, which number does green stand for?
  7. 7.🧮 A 5 V battery is joined to 8 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
  8. 8.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) bigger (d) zero
  9. 9.🔺 A current of 2.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.🔺 A current of 3 A flows when 24 V is joined across a resistor. What is its resistance (in ohms)?
  11. 11.🧾 A 50 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
  12. 12.🧾 A family uses 180 units of electricity in a month and each unit costs ₹7. What is the bill (in ₹)?
  13. 13.📏 How many watts (W) is 2.8 kW?
  14. 14.🔺 A current of 3 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  15. 15.⚡ A 12 W device works on 24 V. What current does it take (in amperes)? =
  16. 16.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.Which of these saves electricity? (a) leave the TV on standby (b) iron one shirt at a time (c) switch off empty rooms (d) use old filament bulbs
  18. 18.🌈 A resistor has the colour bands violet, red, orange. What is its value (in ohms)?
  19. 19.⚡ A 4.8 W device works on 24 V. What current does it take (in amperes)? =
  20. 20.🌈 A resistor has the colour bands blue, black, red. What is its value (in ohms)?
  21. 21.💡 Does it save or waste electricity to close the fridge quickly? (a) wastes electricity (b) saves electricity
  22. 22.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  23. 23.🔍 Which is the odd one out? (a) leave fridge door open (b) use daylight to read (c) set the AC to 24 °C (d) close the fridge quickly
  24. 24.📏 How many kilowatts (kW) is 2750 W? =
  25. 25.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  26. 26.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
  27. 27.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V + I (d) P = V × I
  28. 28.📏 How many ohms (Ω) is 7.5 kΩ?
  29. 29.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  30. 30.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  31. 31.🔺 A current of 0.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.🌈 In the resistor colour code, which number does white stand for?
  33. 33.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it lights brighter (c) it does not light (d) it makes a sound
  34. 34.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a fuse (d) a motor
  35. 35.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) a narrow pipe (c) the flow of water (d) the pipe colour
  36. 36.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to limit the current (d) to make it brighter
  37. 37.📏 How many amperes (A) is 1560 mA? =
  38. 38.🔺 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
  39. 39.🧾 A 100 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
  40. 40.🧾 A 1000 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =

Answer key

  1. 115
  2. 100
  3. R = V ÷ I
  4. 5
  5. 204
  6. 5
  7. 0.5
  8. bigger
  9. 20
  10. 8
  11. 0.2
  12. 1260
  13. 2800
  14. 6
  15. 0.5
  16. 1.2
  17. switch off empty rooms
  18. 72000
  19. 0.2
  20. 6000
  21. saves electricity
  22. cathode (−)
  23. leave fridge door open
  24. 2.75
  25. False
  26. 0.6
  27. P = V × I
  28. 7500
  29. 1840
  30. 25
  31. 2
  32. 9
  33. it does not light
  34. a motor
  35. the flow of water
  36. to limit the current
  37. 1.56
  38. V = I × R
  39. 0.8
  40. 10

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