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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 346 · 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.🔺 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
  2. 2.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  3. 3.⚡ A 3 W device works on 3 V. What current does it take (in amperes)? =
  4. 4.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) more than either one (d) less than either one
  5. 5.🔺 A current of 0.5 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  6. 6.🔺 A current of 1 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
  8. 8.🌈 In the resistor colour code, which number does orange stand for?
  9. 9.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 watt (d) 1 ampere
  10. 10.Which of these saves electricity? (a) run fans in empty rooms (b) leave the TV on standby (c) use LED lamps (d) iron one shirt at a time
  11. 11.What does an LED do? (a) lets current go one way (b) has coloured bands (c) glows using little power (d) makes a beeping sound
  12. 12.🌈 A resistor has the colour bands yellow, blue, yellow. What is its value in kilo-ohms (kΩ)? =
  13. 13.🔺 A current of 3 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  15. 15.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a candle (c) an LED lamp (d) a filament bulb
  16. 16.🔺 A current of 0.25 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🌈 In the resistor colour code, which number does yellow stand for?
  18. 18.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
  20. 20.🧮 Resistors of 330 Ω, 20 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
  21. 21.True or false: an LED boosts a small signal. (a) False (b) True
  22. 22.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
  23. 23.💡 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?
  24. 24.Which of these saves electricity? (a) run fans in empty rooms (b) iron one shirt at a time (c) use daylight to read (d) leave the TV on standby
  25. 25.🌈 A resistor has the colour bands red, green, yellow. What is its value in kilo-ohms (kΩ)? =
  26. 26.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
  27. 27.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the length of a wire (d) the colour of light
  28. 28.📏 How many ohms (Ω) is 4.7 kΩ?
  29. 29.What does an LDR do? (a) makes a beeping sound (b) senses how hot it is (c) boosts a small signal (d) senses how bright it is
  30. 30.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets bigger (d) gets smaller
  31. 31.🔺 A current of 1.5 A flows when 22.5 V is joined across a resistor. What is its resistance (in ohms)?
  32. 32.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.🔺 A current of 40 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
  34. 34.Which of these wastes electricity? (a) use daylight to read (b) set the AC to 24 °C (c) run fans in empty rooms (d) switch off empty rooms
  35. 35.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  36. 36.💡 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
  37. 37.🧩 Which component smooths a wobbly supply? (a) resistor (b) capacitor (c) fuse (d) LDR
  38. 38.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 0 % (d) 50 %
  39. 39.🔺 A current of 0.1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🔺 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

Answer key

  1. V = I × R
  2. cathode (−)
  3. 1
  4. less than either one
  5. 6
  6. 20
  7. False
  8. 3
  9. 1 kilowatt-hour (kWh)
  10. use LED lamps
  11. glows using little power
  12. 460
  13. 36
  14. False
  15. an LED lamp
  16. 1.5
  17. 4
  18. 5
  19. 340
  20. 360
  21. False
  22. voltmeter
  23. 200
  24. use daylight to read
  25. 250
  26. 170
  27. energy used each second
  28. 4700
  29. senses how bright it is
  30. gets smaller
  31. 15
  32. 60
  33. 10
  34. run fans in empty rooms
  35. 5
  36. to limit the current
  37. capacitor
  38. 5 %
  39. 0.2
  40. R = V ÷ I

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