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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 381 · 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 4 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  2. 2.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V ÷ I (c) R = V + I (d) R = V × I
  3. 3.🔺 A 16.5 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
  4. 4.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  5. 5.🧩 Which component stores a little charge? (a) capacitor (b) LDR (c) fuse (d) motor
  6. 6.True or false: on an LED, the shorter leg is the anode (+). (a) False (b) True
  7. 7.True or false: to leave fridge door open saves electricity. (a) False (b) True
  8. 8.🔺 A 4 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  9. 9.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets smaller (d) gets bigger
  10. 10.True or false: a buzzer lets current go one way. (a) True (b) False
  11. 11.🧩 A capacitor in a circuit can … (a) spin a wheel (b) measure heat (c) store charge briefly (d) make light
  12. 12.Which of these is measured in amperes (A)? (a) the flow of charge (b) voltage (c) resistance (d) the push of a cell
  13. 13.🌈 A resistor has the colour bands violet, black, red. What is its value in kilo-ohms (kΩ)? =
  14. 14.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 910 Ω resistor? (a) white-brown-red (b) brown-white-brown (c) white-brown-black (d) white-brown-brown
  15. 15.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 3 V supply. What current flows (in mA)?
  16. 16.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it does not light (d) it changes colour
  17. 17.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 4 V supply. What current flows (in mA)?
  18. 18.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?
  19. 19.🔺 A current of 0.5 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  20. 20.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
  21. 21.🧮 Resistors of 68 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
  22. 22.⚡ A device works on 6 V and takes 2 A. What is its power (in watts)? =
  23. 23.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  24. 24.🔺 A 20 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  25. 25.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) the pipe colour (c) a narrow pipe (d) the flow of water
  26. 26.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) always zero (c) their sum (d) more than either one
  27. 27.Which of these wastes electricity? (a) set the AC to 24 °C (b) switch off empty rooms (c) run fans in empty rooms (d) use daylight to read
  28. 28.True or false: a motor turns a fan or wheels. (a) True (b) False
  29. 29.What does an LED do? (a) beeps for an alarm (b) glows using little power (c) senses how bright it is (d) makes things spin
  30. 30.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  31. 31.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to change its colour (c) to store charge (d) to make it brighter
  32. 32.🔺 A current of 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.Which of these is measured in watts (W)? (a) voltage (b) power (c) current (d) resistance
  34. 34.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  35. 35.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
  36. 36.🔺 A current of 3 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  37. 37.⚡ A device works on 12 V and takes 3 A. What is its power (in watts)? =
  38. 38.Which of these is measured in ohms (Ω)? (a) energy used each second (b) current (c) how much a part resists (d) power
  39. 39.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🔺 A 12 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =

Answer key

  1. 40
  2. R = V ÷ I
  3. 50
  4. 1
  5. capacitor
  6. False
  7. False
  8. 2
  9. gets smaller
  10. False
  11. store charge briefly
  12. the flow of charge
  13. 7
  14. white-brown-brown
  15. 5
  16. it does not light
  17. 10
  18. 34
  19. 10
  20. 1.5
  21. 115
  22. 12
  23. 100
  24. 2.5
  25. the flow of water
  26. less than either one
  27. run fans in empty rooms
  28. True
  29. glows using little power
  30. 1840
  31. to limit the current
  32. 6
  33. power
  34. 25
  35. 10
  36. 9
  37. 36
  38. how much a part resists
  39. 6
  40. 3

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