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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 342 · 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 12 W device works on 24 V. What current does it take (in amperes)? =
  2. 2.What does a fuse do? (a) senses how hot it is (b) limits the current (c) blows if current is high (d) stores a little charge
  3. 3.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  4. 4.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  5. 5.🌈 A resistor has the colour bands red, brown, brown. What is its value (in ohms)?
  6. 6.🔺 A current of 0.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.Which of these is measured in amperes (A)? (a) voltage (b) the push of a cell (c) power (d) current
  8. 8.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) lights up (c) may burn out
  9. 9.💡 A red LED uses 2 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  10. 10.🌈 A resistor has the colour bands green, white, brown. What is its value (in ohms)?
  11. 11.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  12. 12.True or false: a diode has coloured bands. (a) True (b) False
  13. 13.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I ÷ R (c) V = I + R (d) V = I × R
  14. 14.🔺 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
  15. 15.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a capacitor (d) a buzzer
  16. 16.🔺 A current of 50 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🔺 A current of 50 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.🔺 A current of 0.25 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.💡 An LED is joined to a 3 V battery through a 220 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) does not light (b) lights up (c) may burn out
  20. 20.Which of these is measured in watts (W)? (a) current (b) power (c) resistance (d) voltage
  21. 21.🔺 A current of 2.5 A flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  22. 22.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 volt (c) 1 watt (d) 1 kilowatt-hour (kWh)
  23. 23.🔺 A current of 40 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
  24. 24.🧮 A 50 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  25. 25.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the widest gap (d) the gold band
  26. 26.🧩 A capacitor in a circuit can … (a) spin a wheel (b) measure heat (c) make light (d) store charge briefly
  27. 27.📏 Which unit measures the push of a cell? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
  28. 28.📏 How many milliamperes (mA) is 0.99 A?
  29. 29.🧮 A 220 Ω resistor is joined in series with two equal 200 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  30. 30.🧮 Resistors of 22 Ω, 33 Ω, 100 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
  31. 31.What does a thermistor do? (a) beeps for an alarm (b) lets current go one way (c) senses how hot it is (d) turns a fan or wheels
  32. 32.True or false: a resistor beeps for an alarm. (a) False (b) True
  33. 33.🔺 A current of 1 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  34. 34.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) an LED (d) a fuse
  35. 35.📏 Which unit measures current? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
  36. 36.🔺 A 5 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
  37. 37.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
  38. 38.🔺 A current of 0.2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  39. 39.💡 An LED is joined to a 6 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) may burn out (c) does not light
  40. 40.True or false: the ammeter measures voltage. (a) False (b) True

Answer key

  1. 0.5
  2. blows if current is high
  3. cathode (−)
  4. 80
  5. 210
  6. 2
  7. current
  8. may burn out
  9. 1000
  10. 590
  11. False
  12. False
  13. V = I × R
  14. I = V ÷ R
  15. a buzzer
  16. 25
  17. 120
  18. 1.5
  19. does not light
  20. power
  21. 4
  22. 1 kilowatt-hour (kWh)
  23. 200
  24. 70
  25. the one nearest an end
  26. store charge briefly
  27. volt (V)
  28. 990
  29. 320
  30. 305
  31. senses how hot it is
  32. False
  33. 20
  34. a motor
  35. ampere (A)
  36. 25
  37. gets smaller
  38. 4
  39. may burn out
  40. False

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