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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 13 · 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 = V × I (d) P = I ÷ V
  2. 2.Which of these is measured in volts (V)? (a) energy used each second (b) how much a part resists (c) current (d) the push of a cell
  3. 3.🔍 Which is the odd one out? (a) switch off empty rooms (b) run fans in empty rooms (c) unplug idle chargers (d) set the AC to 24 °C
  4. 4.📏 How many amperes (A) is 1140 mA? =
  5. 5.True or false: voltage is measured in volts (V). (a) False (b) True
  6. 6.💡 Does it save or waste electricity to leave fridge door open? (a) wastes electricity (b) saves electricity
  7. 7.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  8. 8.📏 Which unit measures current? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
  9. 9.🔺 A current of 0.1 A flows when 0.3 V is joined across a resistor. What is its resistance (in ohms)?
  10. 10.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.True or false: a thermistor senses how hot it is. (a) True (b) False
  12. 12.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to limit the current (d) to store charge
  13. 13.🔺 A 6 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
  14. 14.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = R ÷ I (c) V = I × R (d) V = I ÷ R
  15. 15.🧮 A 1.8 V battery is joined to 5 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
  16. 16.💡 An LED is joined to a 12 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) lights up (c) does not light
  17. 17.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  18. 18.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  19. 19.🔺 A current of 0.2 A flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
  20. 20.🔺 A current of 20 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🔺 A current of 1.5 A flows when 9 V is joined across a resistor. What is its resistance (in ohms)?
  22. 22.🔺 A current of 1.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  23. 23.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets bigger (c) gets smaller (d) becomes zero
  24. 24.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) the flow of water (c) the pipe colour (d) a narrow pipe
  25. 25.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  26. 26.🧩 Which part changes electrical energy into sound? (a) a diode (b) a buzzer (c) a resistor (d) a capacitor
  27. 27.True or false: to unplug idle chargers saves electricity. (a) True (b) False
  28. 28.🌈 A resistor has the colour bands violet, green, red. What is its value (in ohms)?
  29. 29.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  30. 30.🔺 A current of 3 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  31. 31.Which of these wastes electricity? (a) run fans in empty rooms (b) use daylight to read (c) close the fridge quickly (d) unplug idle chargers
  32. 32.🔺 A current of 0.2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.🌈 A resistor has the colour bands violet, black, yellow. What is its value in kilo-ohms (kΩ)? =
  34. 34.🧮 A 22 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  35. 35.🔺 A 5.5 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
  36. 36.⚡ A 36 W device works on 24 V. What current does it take (in amperes)? =
  37. 37.🔺 A current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  38. 38.True or false: to unplug idle chargers wastes electricity. (a) False (b) True
  39. 39.🧩 Which component senses how bright it is? (a) fuse (b) potentiometer (c) LED (d) LDR
  40. 40.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. P = V × I
  2. the push of a cell
  3. run fans in empty rooms
  4. 1.14
  5. True
  6. wastes electricity
  7. 10
  8. ampere (A)
  9. 3
  10. 4
  11. True
  12. to limit the current
  13. 20
  14. V = I × R
  15. 0.2
  16. may burn out
  17. 100
  18. 230
  19. 12
  20. 6.6
  21. 6
  22. 9
  23. gets smaller
  24. the flow of water
  25. 5
  26. a buzzer
  27. True
  28. 7500
  29. 4
  30. 5
  31. run fans in empty rooms
  32. 1
  33. 700
  34. 47
  35. 25
  36. 1.5
  37. 5
  38. False
  39. LDR
  40. 1.5

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