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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 730 · 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 formula gives electric power? (a) P = V + I (b) P = V × I (c) P = V ÷ I (d) P = I ÷ V
  2. 2.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  3. 3.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 0 % (c) 25 % (d) 5 %
  4. 4.🔺 A current of 20 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  5. 5.📏 How many amperes (A) is 360 mA? =
  6. 6.🧩 Which component has coloured bands? (a) resistor (b) potentiometer (c) LDR (d) buzzer
  7. 7.Which of these saves electricity? (a) use old filament bulbs (b) leave the TV on standby (c) leave fridge door open (d) unplug idle chargers
  8. 8.⚡ A 0.15 W device works on 1.5 V. What current does it take (in amperes)? =
  9. 9.🧩 Which component turns a fan or wheels? (a) LDR (b) potentiometer (c) LED (d) motor
  10. 10.🔺 A current of 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = I ÷ V (d) R = V ÷ I
  12. 12.🔺 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
  13. 13.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
  14. 14.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
  15. 15.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  16. 16.🔺 A current of 0.1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🧮 A 150 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  18. 18.🧩 A capacitor in a circuit can … (a) make light (b) measure heat (c) spin a wheel (d) store charge briefly
  19. 19.True or false: the voltmeter is joined in series. (a) True (b) False
  20. 20.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
  21. 21.🧮 A 5.5 V battery is joined to 8 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
  22. 22.🌈 A resistor has the colour bands white, white, red. What is its value (in ohms)?
  23. 23.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a diode (c) a resistor (d) a buzzer
  24. 24.📏 How many kilowatts (kW) is 750 W? =
  25. 25.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  26. 26.🔺 A current of 2.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  27. 27.🌈 In the resistor colour code, which number does brown stand for?
  28. 28.🧮 A 2 V battery is joined to 5 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
  29. 29.What does a capacitor do? (a) glows using little power (b) makes a beeping sound (c) stores a little charge (d) turns a fan or wheels
  30. 30.🧮 Resistors of 33 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
  31. 31.🔺 A current of 50 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  32. 32.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 volt (c) 1 ampere (d) 1 watt
  33. 33.📏 How many kilo-ohms (kΩ) is 8700 Ω? =
  34. 34.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = R ÷ I (c) V = I ÷ R (d) V = I × R
  35. 35.📏 How many watts (W) is 3.2 kW?
  36. 36.📏 How many amperes (A) is 1550 mA? =
  37. 37.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
  38. 38.💡 What does LED stand for? (a) large electric dial (b) light-emitting diode (c) light energy dial (d) low energy device
  39. 39.🔺 A current of 2.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.⚡ A device works on 12 V and takes 0.5 A. What is its power (in watts)? =

Answer key

  1. P = V × I
  2. cathode (−)
  3. 5 %
  4. 250
  5. 0.36
  6. resistor
  7. unplug idle chargers
  8. 0.1
  9. motor
  10. 6
  11. R = V ÷ I
  12. I = V ÷ R
  13. less than either one
  14. voltmeter
  15. False
  16. 0.6
  17. 315
  18. store charge briefly
  19. False
  20. to limit the current
  21. 0.5
  22. 9900
  23. a buzzer
  24. 0.75
  25. 200
  26. 10
  27. 1
  28. 0.25
  29. stores a little charge
  30. 66
  31. 200
  32. 1 kilowatt-hour (kWh)
  33. 8.7
  34. V = I × R
  35. 3200
  36. 1.55
  37. 15
  38. light-emitting diode
  39. 5
  40. 6

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