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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 559 · 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.🧮 Three equal 150 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  2. 2.📏 Which unit measures resistance? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
  3. 3.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  4. 4.🌈 A resistor has the colour bands red, orange, red. What is its value (in ohms)?
  5. 5.📏 How many kilowatts (kW) is 950 W? =
  6. 6.🔺 A current of 20 mA flows when 9.4 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.🔺 A current of 1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity
  9. 9.💡 A red LED uses 2 V and should get 10 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  10. 10.🔺 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
  11. 11.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
  12. 12.📏 How many milliamperes (mA) is 1.37 A?
  13. 13.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a diode (c) a resistor (d) a capacitor
  14. 14.⚡ A device works on 5 V and takes 3 A. What is its power (in watts)? =
  15. 15.🧩 Which component boosts a small signal? (a) LED (b) transistor (c) resistor (d) thermistor
  16. 16.📏 How many ohms (Ω) is 8.4 kΩ?
  17. 17.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  18. 18.🌈 A resistor has the colour bands brown, grey, orange. What is its value (in ohms)?
  19. 19.🔺 A current of 40 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
  20. 20.🔺 A current of 3 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🧮 Resistors of 20 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
  22. 22.🌈 In the resistor colour code, which number does brown stand for?
  23. 23.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to limit the current (d) to store charge
  24. 24.🧩 Which component turns a fan or wheels? (a) capacitor (b) motor (c) buzzer (d) diode
  25. 25.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 0 % (d) 25 %
  26. 26.🌈 A resistor has the colour bands yellow, white, orange. What is its value in kilo-ohms (kΩ)? =
  27. 27.Which of these saves electricity? (a) run fans in empty rooms (b) leave the TV on standby (c) leave fridge door open (d) unplug idle chargers
  28. 28.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  29. 29.⚡ A device works on 1.5 V and takes 0.2 A. What is its power (in watts)? =
  30. 30.⚡ A device works on 24 V and takes 0.25 A. What is its power (in watts)? =
  31. 31.🔺 A current of 40 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  32. 32.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
  33. 33.🧩 Which component senses how bright it is? (a) motor (b) fuse (c) LDR (d) diode
  34. 34.🔺 A 3 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  35. 35.📏 In the water-pipe picture of a circuit, current is like … (a) the flow of water (b) the water pressure (c) the pipe colour (d) a narrow pipe
  36. 36.True or false: voltage is measured in volts (V). (a) False (b) True
  37. 37.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
  38. 38.📏 In the water-pipe picture of a circuit, voltage is like … (a) the pipe colour (b) the water pressure (c) the tap handle (d) the water tank lid
  39. 39.Which of these saves electricity? (a) leave fridge door open (b) run fans in empty rooms (c) leave the TV on standby (d) set the AC to 24 °C
  40. 40.True or false: a buzzer senses how hot it is. (a) False (b) True

Answer key

  1. 50
  2. ohm (Ω)
  3. cathode (−)
  4. 2300
  5. 0.95
  6. 470
  7. 2
  8. wastes electricity
  9. 400
  10. I = V ÷ R
  11. 1.5
  12. 1370
  13. a buzzer
  14. 15
  15. transistor
  16. 8400
  17. 20
  18. 18000
  19. 12
  20. 18
  21. 40
  22. 1
  23. to limit the current
  24. motor
  25. 5 %
  26. 49
  27. unplug idle chargers
  28. 115
  29. 0.3
  30. 6
  31. 250
  32. False
  33. LDR
  34. 1.5
  35. the flow of water
  36. True
  37. 315
  38. the water pressure
  39. set the AC to 24 °C
  40. False

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