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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 449 · 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.🧮 A 3.5 V battery is joined to 2 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
  2. 2.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
  3. 3.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 watt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
  4. 4.⚡ A device works on 3 V and takes 2 A. What is its power (in watts)? =
  5. 5.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to limit the current (d) to change its colour
  6. 6.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  7. 7.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  9. 9.🔺 An 11.75 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  10. 10.True or false: a potentiometer turns a fan or wheels. (a) True (b) False
  11. 11.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  12. 12.🌈 In the resistor colour code, which number does green stand for?
  13. 13.True or false: a motor limits the current. (a) False (b) True
  14. 14.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  15. 15.True or false: a buzzer smooths a wobbly supply. (a) True (b) False
  16. 16.🌈 A resistor has the colour bands white, violet, red. What is its value in kilo-ohms (kΩ)? =
  17. 17.🔺 A current of 0.2 A flows when 1.6 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.True or false: a motor turns a fan or wheels. (a) False (b) True
  19. 19.🔺 A current of 50 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  20. 20.⚡ A device works on 12 V and takes 1 A. What is its power (in watts)? =
  21. 21.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
  22. 22.What does a buzzer do? (a) blows if current is high (b) senses how bright it is (c) beeps for an alarm (d) limits the current
  23. 23.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  24. 24.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 5 % (d) 0 %
  25. 25.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 84 Ω resistor? (a) yellow-grey-black (b) white-yellow-black (c) grey-yellow-brown (d) grey-yellow-black
  26. 26.🌈 A resistor has the colour bands orange, grey, orange. What is its value (in ohms)?
  27. 27.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) gets bigger (d) stays the same
  28. 28.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  30. 30.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
  31. 31.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  32. 32.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it makes a sound (c) it lights brighter (d) it does not light
  33. 33.🔍 Which is the odd one out? (a) use old filament bulbs (b) leave fridge door open (c) set the AC to 24 °C (d) leave the TV on standby
  34. 34.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a capacitor (c) a buzzer (d) a diode
  35. 35.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.📏 Which unit measures resistance? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
  37. 37.True or false: a thermistor makes things spin. (a) True (b) False
  38. 38.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the colour of light (d) the size of a cell
  39. 39.🔺 A current of 1.5 A flows when 4.5 V is joined across a resistor. What is its resistance (in ohms)?
  40. 40.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = I ÷ V (d) P = V + I

Answer key

  1. 0.5
  2. False
  3. 1 kilowatt-hour (kWh)
  4. 6
  5. to limit the current
  6. 160
  7. 2.4
  8. anode (+)
  9. 25
  10. False
  11. 345
  12. 5
  13. False
  14. 300
  15. False
  16. 9.7
  17. 8
  18. True
  19. 11
  20. 12
  21. ammeter
  22. beeps for an alarm
  23. cathode (−)
  24. 5 %
  25. grey-yellow-black
  26. 38000
  27. gets smaller
  28. 6
  29. 5
  30. voltmeter
  31. 120
  32. it does not light
  33. set the AC to 24 °C
  34. a buzzer
  35. 4
  36. ohm (Ω)
  37. False
  38. energy used each second
  39. 3
  40. P = V × I

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