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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 911 · 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 blue LED uses 3 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  2. 2.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?
  3. 3.True or false: to close the fridge quickly wastes electricity. (a) True (b) False
  4. 4.True or false: to leave fridge door open wastes electricity. (a) True (b) False
  5. 5.💡 An LED is joined to a 5 V battery through a 330 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) may burn out (b) lights up (c) does not light
  6. 6.True or false: a buzzer makes things spin. (a) True (b) False
  7. 7.🔺 A current of 0.1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.True or false: the ammeter measures voltage. (a) True (b) False
  9. 9.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 50 % (d) 0 %
  10. 10.Which of these is measured in amperes (A)? (a) voltage (b) the push of a cell (c) resistance (d) current
  11. 11.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 54000 Ω resistor? (a) green-yellow-red (b) green-yellow-orange (c) yellow-green-orange (d) green-yellow-yellow
  12. 12.🔺 A 0.3 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  13. 13.🔺 A current of 25 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  14. 14.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  15. 15.🔺 A 4.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  16. 16.What does a thermistor do? (a) blows if current is high (b) senses how hot it is (c) stores a little charge (d) smooths a wobbly supply
  17. 17.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
  18. 18.🔺 A 4 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  19. 19.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
  20. 20.⚡ A 3 W device works on 12 V. What current does it take (in amperes)? =
  21. 21.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
  22. 22.What does a transistor do? (a) senses how bright it is (b) boosts a small signal (c) is a resistance knob (d) limits the current
  23. 23.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I ÷ R (c) V = R ÷ I (d) V = I × R
  24. 24.🔺 A current of 0.5 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
  25. 25.🧮 Resistors of 47 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
  26. 26.🔍 Which is the odd one out? (a) leave the TV on standby (b) leave fridge door open (c) set the AC to 24 °C (d) run fans in empty rooms
  27. 27.True or false: the ammeter is joined across a part. (a) False (b) True
  28. 28.🔺 A 4 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  29. 29.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
  30. 30.🧮 A 68 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  31. 31.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) a bigger tank (c) the flow of water (d) the water pressure
  32. 32.⚡ A device works on 5 V and takes 1 A. What is its power (in watts)? =
  33. 33.True or false: an LDR senses how bright it is. (a) True (b) False
  34. 34.📏 Which unit measures energy used each second? (a) volt (V) (b) ampere (A) (c) ohm (Ω) (d) watt (W)
  35. 35.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.🔺 A current of 50 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  37. 37.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) gets smaller (d) becomes zero
  38. 38.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a buzzer (d) a capacitor
  39. 39.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
  40. 40.🔺 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

Answer key

  1. 600
  2. 20
  3. False
  4. True
  5. does not light
  6. False
  7. 0.4
  8. False
  9. 5 %
  10. current
  11. green-yellow-orange
  12. 0.1
  13. 400
  14. 10
  15. 1.5
  16. senses how hot it is
  17. True
  18. 0.2
  19. True
  20. 0.25
  21. store charge briefly
  22. boosts a small signal
  23. V = I × R
  24. 4
  25. 57
  26. set the AC to 24 °C
  27. False
  28. 2
  29. a motor
  30. 568
  31. a narrow pipe
  32. 5
  33. True
  34. watt (W)
  35. 5
  36. 16.5
  37. gets smaller
  38. a buzzer
  39. True
  40. I = V ÷ R

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