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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 409 · 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.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) more than either one (d) their sum
  2. 2.🔺 A current of 0.1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  3. 3.🔺 A current of 3 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 3 V supply. What current flows (in mA)?
  5. 5.🧮 A 2.4 V battery is joined to 2 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
  6. 6.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.🧩 Which component makes a beeping sound? (a) motor (b) capacitor (c) buzzer (d) LED
  8. 8.🧾 A 50 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
  9. 9.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) smaller (d) stay the same
  10. 10.Which of these saves electricity? (a) leave fridge door open (b) leave the TV on standby (c) switch off empty rooms (d) iron one shirt at a time
  11. 11.🔺 A current of 1.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  12. 12.💡 A red LED uses 2 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  13. 13.🔺 A 30 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  14. 14.🔺 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
  15. 15.🧮 Resistors of 10 Ω, 47 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
  16. 16.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 50 % (d) 25 %
  17. 17.True or false: on an LED, the shorter leg is the anode (+). (a) False (b) True
  18. 18.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it does not light (c) it changes colour (d) it lights brighter
  19. 19.🔺 A current of 10 mA flows when 1.5 V is joined across a resistor. What is its resistance (in ohms)?
  20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 18 Ω resistor? (a) grey-brown-black (b) brown-grey-black (c) red-grey-black (d) brown-grey-brown
  21. 21.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  22. 22.What does a buzzer do? (a) senses how hot it is (b) makes a beeping sound (c) stores a little charge (d) makes things spin
  23. 23.Which of these saves electricity? (a) leave the TV on standby (b) set the AC to 24 °C (c) iron one shirt at a time (d) leave fridge door open
  24. 24.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
  25. 25.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) the size of a cell (d) energy used each second
  26. 26.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
  27. 27.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  28. 28.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  29. 29.🌈 In the resistor colour code, which number does black stand for?
  30. 30.🔺 A current of 25 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
  31. 31.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = V ÷ I (d) P = I ÷ V
  33. 33.⚡ A device works on 1.5 V and takes 1.5 A. What is its power (in watts)? =
  34. 34.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.⚡ A device works on 1.5 V and takes 0.2 A. What is its power (in watts)? =
  36. 36.📏 How many kilowatts (kW) is 2700 W? =
  37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 90 Ω resistor? (a) brown-black-black (b) white-black-brown (c) white-black-black (d) brown-white-black
  38. 38.⚡ A 0.375 W device works on 1.5 V. What current does it take (in amperes)? =
  39. 39.True or false: the ammeter is joined across a part. (a) True (b) False
  40. 40.True or false: to switch off empty rooms wastes electricity. (a) True (b) False

Answer key

  1. less than either one
  2. 0.4
  3. 30
  4. 5
  5. 0.2
  6. 8
  7. buzzer
  8. 0.3
  9. bigger
  10. switch off empty rooms
  11. 9
  12. 700
  13. 1.5
  14. I = V ÷ R
  15. 77
  16. 5 %
  17. False
  18. it does not light
  19. 150
  20. brown-grey-black
  21. 10
  22. makes a beeping sound
  23. set the AC to 24 °C
  24. voltmeter
  25. energy used each second
  26. 460
  27. False
  28. anode (+)
  29. 0
  30. 300
  31. 4.4
  32. P = V × I
  33. 2.25
  34. 2.4
  35. 0.3
  36. 2.7
  37. white-black-black
  38. 0.25
  39. False
  40. False

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