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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 435 · 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 resistor has the colour bands brown, green, red. What is its value (in ohms)?
  2. 2.⚡ A 1.2 W device works on 12 V. What current does it take (in amperes)? =
  3. 3.True or false: power is measured in amperes (A). (a) True (b) False
  4. 4.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V ÷ I (d) P = V × I
  5. 5.What does a thermistor do? (a) senses how hot it is (b) limits the current (c) smooths a wobbly supply (d) makes a beeping sound
  6. 6.🔺 A current of 10 mA flows when 4.7 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the colour of light (d) the length of a wire
  8. 8.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
  9. 9.🔺 A 10 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
  10. 10.True or false: to switch off empty rooms saves electricity. (a) False (b) True
  11. 11.True or false: voltage is measured in volts (V). (a) True (b) False
  12. 12.🌈 A resistor has the colour bands red, brown, red. What is its value in kilo-ohms (kΩ)? =
  13. 13.🔺 A 0.8 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
  14. 14.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  15. 15.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
  16. 16.🔺 A current of 1.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 68 Ω resistor? (a) blue-grey-brown (b) grey-blue-black (c) violet-grey-black (d) blue-grey-black
  18. 18.🔺 A current of 0.1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  20. 20.🔺 A current of 0.2 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) zero (d) smaller
  22. 22.💡 Why does an LED need a resistor in series? (a) to store charge (b) to change its colour (c) to limit the current (d) to make it brighter
  23. 23.🧩 Which component senses how bright it is? (a) thermistor (b) LDR (c) motor (d) diode
  24. 24.🌈 A resistor has the colour bands brown, green, brown. What is its value (in ohms)?
  25. 25.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  26. 26.🧾 A family uses 50 units of electricity in a month and each unit costs ₹5. What is the bill (in ₹)?
  27. 27.True or false: the flow of charge is measured in amperes (A). (a) True (b) False
  28. 28.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
  29. 29.🔺 A current of 25 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  30. 30.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = I ÷ V (d) R = V ÷ I
  31. 31.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
  32. 32.True or false: a motor senses how bright it is. (a) True (b) False
  33. 33.📏 How many kilo-ohms (kΩ) is 1700 Ω? =
  34. 34.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
  35. 35.🔺 A current of 3 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
  36. 36.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  37. 37.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
  38. 38.Which of these is measured in volts (V)? (a) energy used each second (b) the push of a cell (c) current (d) resistance
  39. 39.True or false: resistance is measured in ohms (Ω). (a) False (b) True
  40. 40.🌈 A resistor has the colour bands orange, violet, orange. What is its value in kilo-ohms (kΩ)? =

Answer key

  1. 1500
  2. 0.1
  3. False
  4. P = V × I
  5. senses how hot it is
  6. 470
  7. energy used each second
  8. False
  9. 40
  10. True
  11. True
  12. 2.1
  13. 0.2
  14. 25
  15. saves electricity
  16. 12
  17. blue-grey-black
  18. 0.8
  19. 0.8
  20. 1.2
  21. bigger
  22. to limit the current
  23. LDR
  24. 150
  25. anode (+)
  26. 250
  27. True
  28. 460
  29. 400
  30. R = V ÷ I
  31. 272
  32. False
  33. 1.7
  34. 20
  35. 10
  36. 1840
  37. a motor
  38. the push of a cell
  39. True
  40. 37

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