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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 296 · 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.What does an LED do? (a) glows using little power (b) makes things spin (c) turns a fan or wheels (d) blows if current is high
  2. 2.⚡ A device works on 12 V and takes 2 A. What is its power (in watts)? =
  3. 3.📏 Which unit measures power? (a) ohm (Ω) (b) ampere (A) (c) watt (W) (d) volt (V)
  4. 4.🧮 Four equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  5. 5.📏 How many amperes (A) is 1790 mA? =
  6. 6.🌈 A resistor has the colour bands blue, brown, red. What is its value in kilo-ohms (kΩ)? =
  7. 7.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
  8. 8.⚡ A device works on 12 V and takes 0.5 A. What is its power (in watts)? =
  9. 9.🔺 A 4 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
  10. 10.🔺 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
  11. 11.💡 Does it save or waste electricity to run fans in empty rooms? (a) wastes electricity (b) saves electricity
  12. 12.📏 How many amperes (A) is 2400 mA? =
  13. 13.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a capacitor (d) a buzzer
  14. 14.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
  15. 15.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  16. 16.⚡ 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
  17. 17.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  18. 18.⚡ A device works on 6 V and takes 1.5 A. What is its power (in watts)? =
  19. 19.True or false: how much a part resists is measured in amperes (A). (a) True (b) False
  20. 20.🔺 A current of 10 mA flows when 1.2 V is joined across a resistor. What is its resistance (in ohms)?
  21. 21.🧩 Which part changes electrical energy into movement? (a) an LED (b) a fuse (c) a motor (d) a resistor
  22. 22.🧮 Resistors of 20 Ω, 150 Ω, 10 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
  23. 23.🧮 Resistors of 470 Ω, 470 Ω, 68 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
  24. 24.🧾 A 50 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
  25. 25.⚡ A device works on 6 V and takes 0.1 A. What is its power (in watts)? =
  26. 26.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  27. 27.⚡ A 4.5 W device works on 1.5 V. What current does it take (in amperes)? =
  28. 28.🧮 Four equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  29. 29.🔺 A current of 0.1 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  30. 30.True or false: a fuse blows if current is high. (a) True (b) False
  31. 31.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
  32. 32.🔺 A current of 0.2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
  34. 34.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) smaller (c) zero (d) bigger
  35. 35.🔺 A current of 50 mA flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  36. 36.🧾 A 500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
  37. 37.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  38. 38.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
  39. 39.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) stays the same (c) gets bigger (d) becomes zero
  40. 40.🧩 Which component senses how bright it is? (a) LED (b) thermistor (c) LDR (d) diode

Answer key

  1. glows using little power
  2. 24
  3. watt (W)
  4. 50
  5. 1.79
  6. 6.1
  7. 5
  8. 6
  9. 20
  10. V = I × R
  11. wastes electricity
  12. 2.4
  13. a buzzer
  14. 2300
  15. 120
  16. energy used each second
  17. 115
  18. 9
  19. False
  20. 120
  21. a motor
  22. 202
  23. 1055
  24. 0.1
  25. 0.6
  26. 10
  27. 3
  28. 5
  29. 2
  30. True
  31. P = V × I
  32. 4
  33. saves electricity
  34. bigger
  35. 300
  36. 2
  37. 4
  38. voltmeter
  39. gets smaller
  40. LDR

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