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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 207 · 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 150 Ω resistor. What is the voltage across it (in volts)? =
  2. 2.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  3. 3.🔺 A current of 20 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  5. 5.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V × I (c) R = V ÷ I (d) R = I ÷ V
  6. 6.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the size of a cell (d) the length of a wire
  7. 7.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) bigger (d) smaller
  8. 8.🧮 A 7 V battery is joined to 2 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
  9. 9.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 watt (d) 1 ampere
  10. 10.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) measure heat (d) spin a wheel
  11. 11.💡 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?
  12. 12.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
  13. 13.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a motor (c) a resistor (d) an LED
  14. 14.🔍 Which is the odd one out? (a) iron one shirt at a time (b) use old filament bulbs (c) run fans in empty rooms (d) unplug idle chargers
  15. 15.True or false: to iron one shirt at a time saves electricity. (a) False (b) True
  16. 16.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  17. 17.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
  18. 18.True or false: to use daylight to read saves electricity. (a) False (b) True
  19. 19.What does an LDR do? (a) makes a beeping sound (b) limits the current (c) boosts a small signal (d) senses how bright it is
  20. 20.🌈 A resistor has the colour bands red, green, red. What is its value in kilo-ohms (kΩ)? =
  21. 21.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
  22. 22.📏 Which unit measures the push of a cell? (a) ohm (Ω) (b) watt (W) (c) ampere (A) (d) volt (V)
  23. 23.📏 How many watts (W) is 1.7 kW?
  24. 24.🔍 Which is the odd one out? (a) run fans in empty rooms (b) use daylight to read (c) switch off empty rooms (d) unplug idle chargers
  25. 25.🔺 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
  26. 26.🔺 A current of 10 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
  27. 27.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  28. 28.🔺 A 1.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
  29. 29.⚡ A device works on 1.5 V and takes 1 A. What is its power (in watts)? =
  30. 30.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 2.75 V supply. What current flows (in mA)?
  31. 31.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  32. 32.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
  33. 33.⚡ A 0.6 W device works on 3 V. What current does it take (in amperes)? =
  34. 34.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.🧩 Which component has coloured bands? (a) motor (b) LED (c) thermistor (d) resistor
  37. 37.📏 How many kilowatts (kW) is 1400 W? =
  38. 38.💡 A red LED uses 2 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  39. 39.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets bigger (d) gets smaller
  40. 40.True or false: a motor turns a fan or wheels. (a) False (b) True

Answer key

  1. 6
  2. 500
  3. 6.6
  4. 200
  5. R = V ÷ I
  6. energy used each second
  7. bigger
  8. 1
  9. 1 kilowatt-hour (kWh)
  10. store charge briefly
  11. 600
  12. 1150
  13. a motor
  14. unplug idle chargers
  15. False
  16. 25
  17. False
  18. True
  19. senses how bright it is
  20. 2.5
  21. P = V × I
  22. volt (V)
  23. 1700
  24. run fans in empty rooms
  25. V = I × R
  26. 250
  27. 10
  28. 10
  29. 1.5
  30. 5
  31. cathode (−)
  32. saves electricity
  33. 0.2
  34. 1.2
  35. 12.5
  36. resistor
  37. 1.4
  38. 350
  39. gets smaller
  40. True

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