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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 649 · 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.What does a resistor do? (a) senses how hot it is (b) senses how bright it is (c) limits the current (d) boosts a small signal
  2. 2.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  3. 3.True or false: a diode turns a fan or wheels. (a) False (b) True
  4. 4.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  5. 5.🧩 Which component smooths a wobbly supply? (a) LED (b) capacitor (c) buzzer (d) fuse
  6. 6.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.⚡ A 2.5 W device works on 5 V. What current does it take (in amperes)? =
  8. 8.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) zero (d) stay the same
  9. 9.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V + I (d) P = V ÷ I
  10. 10.What does a fuse do? (a) smooths a wobbly supply (b) beeps for an alarm (c) is a resistance knob (d) blows if current is high
  11. 11.🔺 A current of 0.2 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.🔺 A current of 25 mA flows when 8.25 V is joined across a resistor. What is its resistance (in ohms)?
  13. 13.What does a diode do? (a) senses how bright it is (b) makes things spin (c) makes a beeping sound (d) lets current go one way
  14. 14.🧮 A 5.5 V battery is joined to 8 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
  15. 15.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  16. 16.True or false: to use LED lamps wastes electricity. (a) True (b) False
  17. 17.🔺 A 3.75 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
  18. 18.🔺 A current of 0.1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets smaller (d) gets bigger
  20. 20.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  21. 21.⚡ A 0.6 W device works on 3 V. What current does it take (in amperes)? =
  22. 22.True or false: a transistor limits the current. (a) False (b) True
  23. 23.🌈 A resistor has the colour bands yellow, white, red. What is its value in kilo-ohms (kΩ)? =
  24. 24.🧮 A 1.3 V battery is joined to 5 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
  25. 25.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 kilowatt-hour (kWh) (c) 1 volt (d) 1 watt
  26. 26.Which of these wastes electricity? (a) use daylight to read (b) run fans in empty rooms (c) use LED lamps (d) set the AC to 24 °C
  27. 27.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 5 % (d) 0 %
  28. 28.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  29. 29.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
  30. 30.Which of these is measured in amperes (A)? (a) the flow of charge (b) the push of a cell (c) power (d) energy used each second
  31. 31.True or false: energy used each second is measured in ohms (Ω). (a) False (b) True
  32. 32.🧩 Which component turns a fan or wheels? (a) transistor (b) diode (c) resistor (d) motor
  33. 33.True or false: an LDR turns a fan or wheels. (a) True (b) False
  34. 34.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V + R (c) I = V × R (d) I = V ÷ R
  35. 35.🌈 In the resistor colour code, which number does violet stand for?
  36. 36.🌈 A resistor has the colour bands orange, brown, orange. What is its value in kilo-ohms (kΩ)? =
  37. 37.True or false: an LED makes things spin. (a) False (b) True
  38. 38.🔺 A 2.4 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  39. 39.📏 Which unit measures the push of a cell? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
  40. 40.🌈 In the resistor colour code, which number does black stand for?

Answer key

  1. limits the current
  2. 10
  3. False
  4. 20
  5. capacitor
  6. 6
  7. 0.5
  8. bigger
  9. P = V × I
  10. blows if current is high
  11. 4
  12. 330
  13. lets current go one way
  14. 0.5
  15. 25
  16. False
  17. 25
  18. 0.3
  19. gets smaller
  20. 500
  21. 0.2
  22. False
  23. 4.9
  24. 0.1
  25. 1 kilowatt-hour (kWh)
  26. run fans in empty rooms
  27. 5 %
  28. anode (+)
  29. energy used each second
  30. the flow of charge
  31. False
  32. motor
  33. False
  34. I = V ÷ R
  35. 7
  36. 31
  37. False
  38. 20
  39. volt (V)
  40. 0

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