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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 850 · 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.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
  2. 2.🔺 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
  3. 3.Which of these wastes electricity? (a) unplug idle chargers (b) close the fridge quickly (c) leave fridge door open (d) use daylight to read
  4. 4.True or false: energy used each second is measured in volts (V). (a) True (b) False
  5. 5.⚡ A device works on 6 V and takes 1.5 A. What is its power (in watts)? =
  6. 6.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it does not light (c) it changes colour (d) it makes a sound
  7. 7.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
  8. 8.📏 How many milliamperes (mA) is 0.25 A?
  9. 9.🔺 A current of 3 A flows when 24 V is joined across a resistor. What is its resistance (in ohms)?
  10. 10.🔺 A current of 2.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.🌈 In the resistor colour code, which number does black stand for?
  12. 12.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) more than either one (d) their sum
  13. 13.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 50 % (c) 25 % (d) 5 %
  14. 14.🧩 Which component turns a fan or wheels? (a) capacitor (b) LED (c) motor (d) resistor
  15. 15.Which of these is measured in amperes (A)? (a) the flow of charge (b) energy used each second (c) resistance (d) how much a part resists
  16. 16.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a fuse (d) a motor
  17. 17.⚡ A 0.75 W device works on 1.5 V. What current does it take (in amperes)? =
  18. 18.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) gets bigger (c) becomes zero (d) stays the same
  19. 19.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  20. 20.🧾 A 100 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
  21. 21.True or false: a fuse smooths a wobbly supply. (a) False (b) True
  22. 22.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
  23. 23.🔺 A 20 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
  24. 24.True or false: a buzzer makes a beeping sound. (a) True (b) False
  25. 25.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  26. 26.💡 What does LED stand for? (a) low energy device (b) light-emitting diode (c) light energy dial (d) large electric dial
  27. 27.🧩 Which component stores a little charge? (a) LED (b) resistor (c) fuse (d) capacitor
  28. 28.True or false: the ammeter is joined in series. (a) True (b) False
  29. 29.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  30. 30.📏 How many ohms (Ω) is 2 kΩ?
  31. 31.🌈 A resistor has the colour bands blue, brown, orange. What is its value (in ohms)?
  32. 32.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
  33. 33.📏 How many milliamperes (mA) is 0.05 A?
  34. 34.🔺 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
  35. 35.🧾 A 1000 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
  36. 36.🔺 A 2.5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  37. 37.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
  38. 38.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  39. 39.💡 An LED is joined to a 3 V battery through a 1000 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) lights up (b) does not light (c) may burn out
  40. 40.🔺 A current of 50 mA flows when 15 V is joined across a resistor. What is its resistance (in ohms)?

Answer key

  1. P = V × I
  2. V = I × R
  3. leave fridge door open
  4. False
  5. 9
  6. it does not light
  7. 1.5
  8. 250
  9. 8
  10. 5
  11. 0
  12. less than either one
  13. 5 %
  14. motor
  15. the flow of charge
  16. a motor
  17. 0.5
  18. gets smaller
  19. 115
  20. 0.5
  21. False
  22. ammeter
  23. 50
  24. True
  25. 300
  26. light-emitting diode
  27. capacitor
  28. True
  29. 4
  30. 2000
  31. 61000
  32. wastes electricity
  33. 50
  34. R = V ÷ I
  35. 8
  36. 0.25
  37. ammeter
  38. anode (+)
  39. does not light
  40. 300

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