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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 609 · 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 3.75 V battery is joined to 3 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
  2. 2.🧩 Which component is a resistance knob? (a) buzzer (b) LDR (c) potentiometer (d) thermistor
  3. 3.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?
  4. 4.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =
  5. 5.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  6. 6.🔺 A 36 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
  7. 7.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 volt (c) 1 kilowatt-hour (kWh) (d) 1 ampere
  8. 8.🔍 Which is the odd one out? (a) switch off empty rooms (b) unplug idle chargers (c) leave fridge door open (d) use daylight to read
  9. 9.🌈 A resistor has the colour bands white, black, orange. What is its value (in ohms)?
  10. 10.🔺 A current of 1.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
  12. 12.🔺 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
  13. 13.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
  14. 14.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 25 % (c) 50 % (d) 0 %
  15. 15.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
  16. 16.What does a buzzer do? (a) turns a fan or wheels (b) limits the current (c) makes a beeping sound (d) senses how hot it is
  17. 17.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
  18. 18.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an oil lamp (c) an LED lamp (d) a filament bulb
  19. 19.True or false: an LED turns a fan or wheels. (a) False (b) True
  20. 20.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🔺 A 4 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
  22. 22.⚡ A 10 W device works on 5 V. What current does it take (in amperes)? =
  23. 23.⚡ A 4.5 W device works on 3 V. What current does it take (in amperes)? =
  24. 24.🌈 A resistor has the colour bands violet, red, red. What is its value (in ohms)?
  25. 25.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  26. 26.🔺 A 10 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
  27. 27.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
  28. 28.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to limit the current (d) to store charge
  29. 29.🧮 A 4 V battery is joined to 10 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
  30. 30.🧾 A 200 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
  31. 31.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V × R (c) I = V + R (d) I = V ÷ R
  32. 32.⚡ Power tells us … (a) the size of a cell (b) energy used each second (c) the colour of light (d) the length of a wire
  33. 33.🔺 A 30 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  34. 34.True or false: a buzzer boosts a small signal. (a) True (b) False
  35. 35.🔺 A current of 0.25 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.True or false: an LDR blows if current is high. (a) False (b) True
  37. 37.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) always zero (d) less than either one
  38. 38.🌈 Which band is read first on a resistor? (a) any band (b) the widest gap (c) the one nearest an end (d) the gold band
  39. 39.🔺 A current of 25 mA flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
  40. 40.True or false: the ammeter measures voltage. (a) True (b) False

Answer key

  1. 0.25
  2. potentiometer
  3. 306
  4. 0.9
  5. 5
  6. 3
  7. 1 kilowatt-hour (kWh)
  8. leave fridge door open
  9. 90000
  10. 15
  11. 0.2
  12. V = I × R
  13. 460
  14. 5 %
  15. 3
  16. makes a beeping sound
  17. True
  18. an LED lamp
  19. False
  20. 5
  21. 20
  22. 2
  23. 1.5
  24. 7200
  25. 1.2
  26. 50
  27. 1
  28. to limit the current
  29. 0.2
  30. 2
  31. I = V ÷ R
  32. energy used each second
  33. 3
  34. False
  35. 3.75
  36. False
  37. less than either one
  38. the one nearest an end
  39. 500
  40. False

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