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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 751 · 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 happens if an LED is put in backwards? (a) it makes a sound (b) it lights brighter (c) it does not light (d) it changes colour
  2. 2.💡 An LED is joined to a 6 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) lights up (b) does not light (c) may burn out
  3. 3.What does a thermistor do? (a) senses how hot it is (b) stores a little charge (c) makes things spin (d) beeps for an alarm
  4. 4.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  5. 5.🔺 A 24 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  6. 6.🧩 A capacitor in a circuit can … (a) spin a wheel (b) store charge briefly (c) make light (d) measure heat
  7. 7.Which of these wastes electricity? (a) set the AC to 24 °C (b) use LED lamps (c) use daylight to read (d) use old filament bulbs
  8. 8.💡 Does it save or waste electricity to close the fridge quickly? (a) wastes electricity (b) saves electricity
  9. 9.🧩 Which component lets current go one way? (a) fuse (b) diode (c) resistor (d) buzzer
  10. 10.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a capacitor (d) a buzzer
  11. 11.🧮 Resistors of 22 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
  12. 12.💡 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?
  13. 13.🔺 A current of 1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.Which of these wastes electricity? (a) close the fridge quickly (b) run fans in empty rooms (c) set the AC to 24 °C (d) unplug idle chargers
  15. 15.True or false: a diode lets current go one way. (a) False (b) True
  16. 16.Which of these wastes electricity? (a) set the AC to 24 °C (b) leave the TV on standby (c) switch off empty rooms (d) use LED lamps
  17. 17.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
  18. 18.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
  19. 19.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
  20. 20.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
  21. 21.💡 Does it save or waste electricity to iron one shirt at a time? (a) saves electricity (b) wastes electricity
  22. 22.📏 How many kilo-ohms (kΩ) is 2500 Ω? =
  23. 23.📏 How many watts (W) is 2.3 kW?
  24. 24.🔺 A current of 0.25 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  25. 25.🔺 A current of 40 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  26. 26.⚡ A 1.8 W device works on 9 V. What current does it take (in amperes)? =
  27. 27.🧾 A family uses 70 units of electricity in a month and each unit costs ₹5. What is the bill (in ₹)?
  28. 28.📏 How many milliamperes (mA) is 1.87 A?
  29. 29.📏 How many ohms (Ω) is 2.3 kΩ?
  30. 30.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  31. 31.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.🔺 A current of 0.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
  34. 34.🔺 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
  35. 35.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a candle (d) a filament bulb
  36. 36.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 watt (c) 1 kilowatt-hour (kWh) (d) 1 volt
  37. 37.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  38. 38.📏 How many amperes (A) is 850 mA? =
  39. 39.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  40. 40.🧮 Resistors of 10 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?

Answer key

  1. it does not light
  2. does not light
  3. senses how hot it is
  4. 10
  5. 3
  6. store charge briefly
  7. use old filament bulbs
  8. saves electricity
  9. diode
  10. a buzzer
  11. 72
  12. 600
  13. 12
  14. run fans in empty rooms
  15. True
  16. leave the TV on standby
  17. energy used each second
  18. 15
  19. voltmeter
  20. 1
  21. wastes electricity
  22. 2.5
  23. 2300
  24. 0.75
  25. 16
  26. 0.2
  27. 350
  28. 1870
  29. 2300
  30. 0.8
  31. 3
  32. 2.5
  33. 6
  34. R = V ÷ I
  35. an LED lamp
  36. 1 kilowatt-hour (kWh)
  37. 100
  38. 0.85
  39. 300
  40. 340

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