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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 214 · 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 lamp gives the same light for the least power? (a) a filament bulb (b) an LED lamp (c) a candle (d) an oil lamp
  2. 2.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  3. 3.🔺 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
  4. 4.🔺 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
  5. 5.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  6. 6.📏 Which unit measures current? (a) volt (V) (b) ohm (Ω) (c) watt (W) (d) ampere (A)
  7. 7.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity
  8. 8.🔺 A current of 2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.⚡ A device works on 1.5 V and takes 2 A. What is its power (in watts)? =
  10. 10.⚡ A 12 W device works on 24 V. What current does it take (in amperes)? =
  11. 11.🔺 A current of 25 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.Which of these wastes electricity? (a) unplug idle chargers (b) set the AC to 24 °C (c) close the fridge quickly (d) iron one shirt at a time
  13. 13.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
  14. 14.🔺 A current of 40 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  15. 15.What does a transistor do? (a) limits the current (b) beeps for an alarm (c) smooths a wobbly supply (d) boosts a small signal
  16. 16.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  17. 17.True or false: the voltmeter is joined in series. (a) False (b) True
  18. 18.🔺 A 37.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  19. 19.What does an LED do? (a) lets current go one way (b) blows if current is high (c) is a resistance knob (d) glows using little power
  20. 20.📏 How many kilo-ohms (kΩ) is 5300 Ω? =
  21. 21.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
  22. 22.🔺 A 5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  23. 23.True or false: to iron one shirt at a time wastes electricity. (a) True (b) False
  24. 24.🔺 A 12 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
  25. 25.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 watt (d) 1 ampere
  26. 26.⚡ A device works on 6 V and takes 1.5 A. What is its power (in watts)? =
  27. 27.Which of these saves electricity? (a) use LED lamps (b) leave the TV on standby (c) leave fridge door open (d) run fans in empty rooms
  28. 28.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V + R (c) I = R ÷ V (d) I = V × R
  29. 29.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
  30. 30.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  31. 31.True or false: current is measured in ohms (Ω). (a) True (b) False
  32. 32.True or false: a thermistor senses how bright it is. (a) True (b) False
  33. 33.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it does not light (d) it changes colour
  34. 34.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.🔺 A current of 50 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  37. 37.⚡ A 3 W device works on 12 V. What current does it take (in amperes)? =
  38. 38.🔺 A current of 0.2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  39. 39.What does an LDR do? (a) is a resistance knob (b) lets current go one way (c) senses how bright it is (d) blows if current is high
  40. 40.🔺 A current of 20 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. an LED lamp
  2. 2.4
  3. V = I × R
  4. R = V ÷ I
  5. 20
  6. ampere (A)
  7. wastes electricity
  8. 8
  9. 3
  10. 0.5
  11. 120
  12. iron one shirt at a time
  13. energy used each second
  14. 100
  15. boosts a small signal
  16. 115
  17. False
  18. 2.5
  19. glows using little power
  20. 5.3
  21. 4.5
  22. 50
  23. True
  24. 40
  25. 1 kilowatt-hour (kWh)
  26. 9
  27. use LED lamps
  28. I = V ÷ R
  29. True
  30. 3.75
  31. False
  32. False
  33. it does not light
  34. 1
  35. 16.5
  36. 1840
  37. 0.25
  38. 2
  39. senses how bright it is
  40. 10

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