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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 510 · 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.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an LED lamp (c) an oil lamp (d) a candle
  2. 2.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
  3. 3.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  4. 4.📏 How many milliamperes (mA) is 1.82 A?
  5. 5.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  6. 6.🔺 A 1.2 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
  7. 7.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  8. 8.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  9. 9.Which of these is measured in watts (W)? (a) voltage (b) current (c) how much a part resists (d) energy used each second
  10. 10.🧮 Resistors of 10 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
  11. 11.🔺 A current of 10 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  12. 12.🧩 Which component glows using little power? (a) motor (b) thermistor (c) diode (d) LED
  13. 13.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.🔺 A 20 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  15. 15.🔍 Which is the odd one out? (a) leave the TV on standby (b) iron one shirt at a time (c) leave fridge door open (d) use daylight to read
  16. 16.True or false: voltage is measured in volts (V). (a) True (b) False
  17. 17.🔺 A current of 10 mA flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.🔍 Which is the odd one out? (a) leave the TV on standby (b) unplug idle chargers (c) use old filament bulbs (d) iron one shirt at a time
  19. 19.⚡ A 0.3 W device works on 1.5 V. What current does it take (in amperes)? =
  20. 20.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
  21. 21.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 200 Ω resistor? (a) red-black-black (b) red-black-brown (c) red-black-red (d) orange-red-brown
  22. 22.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
  23. 23.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 0 % (d) 5 %
  24. 24.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  25. 25.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
  26. 26.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I × R (c) V = R ÷ I (d) V = I ÷ R
  27. 27.🧾 A 1000 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
  28. 28.Which of these is measured in volts (V)? (a) current (b) energy used each second (c) the flow of charge (d) the push of a cell
  29. 29.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  30. 30.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) smaller (d) bigger
  31. 31.⚡ A device works on 9 V and takes 0.25 A. What is its power (in watts)? =
  32. 32.🧮 A 150 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  33. 33.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a capacitor (d) a buzzer
  34. 34.💡 A red LED uses 2 V and should get 20 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  35. 35.🧩 Which component blows if current is high? (a) fuse (b) potentiometer (c) buzzer (d) resistor
  36. 36.🔺 A current of 2.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  37. 37.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to store charge (d) to limit the current
  38. 38.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  39. 39.⚡ A 15 W device works on 5 V. What current does it take (in amperes)? =
  40. 40.⚡ A device works on 3 V and takes 1.5 A. What is its power (in watts)? =

Answer key

  1. an LED lamp
  2. False
  3. 5
  4. 1820
  5. 4
  6. 0.1
  7. False
  8. 360
  9. energy used each second
  10. 43
  11. 2.2
  12. LED
  13. 1
  14. 2.5
  15. use daylight to read
  16. True
  17. 100
  18. unplug idle chargers
  19. 0.2
  20. voltmeter
  21. red-black-brown
  22. voltmeter
  23. 5 %
  24. 230
  25. True
  26. V = I × R
  27. 5
  28. the push of a cell
  29. 115
  30. bigger
  31. 2.25
  32. 200
  33. a buzzer
  34. 500
  35. fuse
  36. 15
  37. to limit the current
  38. 200
  39. 3
  40. 4.5

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