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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 761 · 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 current of 0.5 A flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
  2. 2.True or false: to switch off empty rooms wastes electricity. (a) True (b) False
  3. 3.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
  4. 4.📏 How many kilo-ohms (kΩ) is 3500 Ω? =
  5. 5.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
  6. 6.Which of these saves electricity? (a) run fans in empty rooms (b) leave the TV on standby (c) use daylight to read (d) use old filament bulbs
  7. 7.🧮 Resistors of 33 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
  8. 8.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the water pressure (c) the flow of water (d) a bigger tank
  9. 9.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  10. 10.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 6800 Ω resistor? (a) blue-grey-orange (b) blue-grey-brown (c) blue-grey-red (d) grey-blue-red
  11. 11.🧩 A capacitor in a circuit can … (a) store charge briefly (b) measure heat (c) make light (d) spin a wheel
  12. 12.⚡ 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
  13. 13.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.💡 An LED is joined to a 5 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) lights up (c) does not light
  15. 15.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 0 % (d) 25 %
  16. 16.True or false: a diode lets current go one way. (a) False (b) True
  17. 17.🧮 Two equal 220 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  18. 18.🔺 A current of 0.2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  20. 20.⚡ An 18 W device works on 12 V. What current does it take (in amperes)? =
  21. 21.🔍 Which is the odd one out? (a) use LED lamps (b) unplug idle chargers (c) run fans in empty rooms (d) close the fridge quickly
  22. 22.📏 Which unit measures energy used each second? (a) ohm (Ω) (b) ampere (A) (c) watt (W) (d) volt (V)
  23. 23.🔺 A current of 2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  24. 24.🔺 A 5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  25. 25.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
  26. 26.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it lights brighter (c) it changes colour (d) it does not light
  27. 27.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V + I (c) P = V × I (d) P = V ÷ I
  28. 28.📏 Which unit measures the flow of charge? (a) volt (V) (b) ohm (Ω) (c) watt (W) (d) ampere (A)
  29. 29.🧩 Which part changes electrical energy into sound? (a) a diode (b) a capacitor (c) a buzzer (d) a resistor
  30. 30.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  31. 31.Which of these wastes electricity? (a) use daylight to read (b) leave fridge door open (c) use LED lamps (d) unplug idle chargers
  32. 32.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  33. 33.True or false: the flow of charge is measured in amperes (A). (a) False (b) True
  34. 34.True or false: a resistor has coloured bands. (a) False (b) True
  35. 35.🔺 A current of 10 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.🔺 A current of 25 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
  37. 37.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an LED lamp (c) an oil lamp (d) a filament bulb
  38. 38.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  39. 39.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
  40. 40.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =

Answer key

  1. 5
  2. False
  3. voltmeter
  4. 3.5
  5. less than either one
  6. use daylight to read
  7. 66
  8. a narrow pipe
  9. cathode (−)
  10. blue-grey-red
  11. store charge briefly
  12. energy used each second
  13. 3.75
  14. may burn out
  15. 5 %
  16. True
  17. 110
  18. 0.4
  19. 1.2
  20. 1.5
  21. run fans in empty rooms
  22. watt (W)
  23. 2
  24. 1
  25. 0.375
  26. it does not light
  27. P = V × I
  28. ampere (A)
  29. a buzzer
  30. 10
  31. leave fridge door open
  32. anode (+)
  33. True
  34. True
  35. 5
  36. 6.25
  37. an LED lamp
  38. 240
  39. wastes electricity
  40. 2.4

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