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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 79 · 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 current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  2. 2.💡 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) may burn out (c) lights up
  3. 3.What does a thermistor do? (a) is a resistance knob (b) beeps for an alarm (c) makes things spin (d) senses how hot it is
  4. 4.🔺 A current of 1 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  5. 5.🔺 A 4.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  6. 6.🔺 A current of 2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.🔺 A 5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4200 Ω resistor? (a) yellow-red-orange (b) yellow-red-red (c) yellow-red-brown (d) red-yellow-red
  9. 9.🔺 A current of 25 mA flows when 3.75 V is joined across a resistor. What is its resistance (in ohms)?
  10. 10.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
  11. 11.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = I ÷ V (c) R = V ÷ I (d) R = V × I
  12. 12.🔍 Which is the odd one out? (a) leave the TV on standby (b) iron one shirt at a time (c) run fans in empty rooms (d) close the fridge quickly
  13. 13.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
  14. 14.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
  15. 15.⚡ A 3 W device works on 1.5 V. What current does it take (in amperes)? =
  16. 16.🔺 A current of 2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🧩 A capacitor in a circuit can … (a) measure heat (b) spin a wheel (c) make light (d) store charge briefly
  18. 18.🔺 A current of 50 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 1400 Ω resistor? (a) yellow-brown-red (b) brown-yellow-brown (c) brown-yellow-orange (d) brown-yellow-red
  20. 20.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to limit the current (d) to store charge
  21. 21.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  22. 22.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  23. 23.True or false: an LDR senses how bright it is. (a) False (b) True
  24. 24.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  25. 25.🧮 Resistors of 33 Ω, 150 Ω, 22 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
  26. 26.🔺 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
  27. 27.🧩 Which component is a resistance knob? (a) capacitor (b) resistor (c) potentiometer (d) motor
  28. 28.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) stay the same (d) zero
  29. 29.🧩 Which component senses how bright it is? (a) LDR (b) transistor (c) capacitor (d) buzzer
  30. 30.💡 What does LED stand for? (a) low energy device (b) light energy dial (c) light-emitting diode (d) large electric dial
  31. 31.🔺 A 3 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  32. 32.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
  33. 33.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
  34. 34.🔺 A current of 0.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 90000 Ω resistor? (a) white-black-yellow (b) white-black-orange (c) brown-white-orange (d) white-black-red
  36. 36.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 100 (c) 1000 (d) 60
  37. 37.🧾 A family uses 180 units of electricity in a month and each unit costs ₹8. What is the bill (in ₹)?
  38. 38.🌈 A resistor has the colour bands white, green, orange. What is its value (in ohms)?
  39. 39.🔺 A current of 3 A flows when 12 V is joined across a resistor. What is its resistance (in ohms)?
  40. 40.🔺 A current of 0.25 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. 18.8
  2. may burn out
  3. senses how hot it is
  4. 15
  5. 1.5
  6. 4
  7. 1
  8. yellow-red-red
  9. 150
  10. 2300
  11. R = V ÷ I
  12. close the fridge quickly
  13. energy used each second
  14. a motor
  15. 2
  16. 6
  17. store charge briefly
  18. 20
  19. brown-yellow-red
  20. to limit the current
  21. cathode (−)
  22. 150
  23. True
  24. 345
  25. 535
  26. V = I × R
  27. potentiometer
  28. bigger
  29. LDR
  30. light-emitting diode
  31. 25
  32. wastes electricity
  33. 1
  34. 5
  35. white-black-orange
  36. 1000
  37. 1440
  38. 95000
  39. 4
  40. 0.75

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