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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 798 · 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 blue LED uses 3 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  2. 2.True or false: resistance is measured in ohms (Ω). (a) True (b) False
  3. 3.🔺 A current of 3 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  5. 5.💡 An LED is joined to a 5 V battery through a 1000 Ω 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
  6. 6.🔺 A current of 50 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.⚡ An 18 W device works on 9 V. What current does it take (in amperes)? =
  8. 8.🔍 Which is the odd one out? (a) use LED lamps (b) switch off empty rooms (c) use daylight to read (d) iron one shirt at a time
  9. 9.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  10. 10.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 72000 Ω resistor? (a) violet-red-yellow (b) violet-red-red (c) red-violet-orange (d) violet-red-orange
  11. 11.True or false: to switch off empty rooms saves electricity. (a) True (b) False
  12. 12.🔺 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
  13. 13.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
  14. 14.🔺 A current of 0.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
  15. 15.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 86000 Ω resistor? (a) grey-blue-yellow (b) grey-blue-red (c) blue-grey-orange (d) grey-blue-orange
  16. 16.🧩 Which component has coloured bands? (a) capacitor (b) motor (c) resistor (d) thermistor
  17. 17.🌈 Which band is read first on a resistor? (a) the gold band (b) the one nearest an end (c) the widest gap (d) any band
  18. 18.Which of these saves electricity? (a) use LED lamps (b) run fans in empty rooms (c) leave the TV on standby (d) leave fridge door open
  19. 19.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  20. 20.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
  21. 21.📏 Which unit measures how much a part resists? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
  22. 22.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
  23. 23.⚡ A 0.75 W device works on 1.5 V. What current does it take (in amperes)? =
  24. 24.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it changes colour (c) it does not light (d) it lights brighter
  25. 25.Which of these is measured in watts (W)? (a) the push of a cell (b) how much a part resists (c) voltage (d) energy used each second
  26. 26.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 1000 (c) 100 (d) 10
  27. 27.🔍 Which is the odd one out? (a) unplug idle chargers (b) use old filament bulbs (c) leave the TV on standby (d) iron one shirt at a time
  28. 28.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🧮 Resistors of 150 Ω, 33 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
  30. 30.🔺 A current of 40 mA flows when 4.8 V is joined across a resistor. What is its resistance (in ohms)?
  31. 31.🧩 Which component turns a fan or wheels? (a) motor (b) diode (c) LED (d) transistor
  32. 32.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an oil lamp (c) an LED lamp (d) a filament bulb
  33. 33.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 24 Ω resistor? (a) red-yellow-brown (b) yellow-red-black (c) red-yellow-black (d) orange-yellow-black
  34. 34.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a motor (d) a fuse
  35. 35.🔺 A current of 40 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.Which of these is measured in amperes (A)? (a) energy used each second (b) voltage (c) the push of a cell (d) the flow of charge
  37. 37.🧩 Which component senses how hot it is? (a) LDR (b) thermistor (c) fuse (d) diode
  38. 38.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  39. 39.🔺 A current of 2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.What does a resistor do? (a) stores a little charge (b) lets current go one way (c) glows using little power (d) limits the current

Answer key

  1. 150
  2. True
  3. 30
  4. anode (+)
  5. lights up
  6. 400
  7. 2
  8. iron one shirt at a time
  9. 345
  10. violet-red-orange
  11. True
  12. V = I × R
  13. gets smaller
  14. 15
  15. grey-blue-orange
  16. resistor
  17. the one nearest an end
  18. use LED lamps
  19. cathode (−)
  20. 0.375
  21. ohm (Ω)
  22. 3
  23. 0.5
  24. it does not light
  25. energy used each second
  26. 1000
  27. unplug idle chargers
  28. 10
  29. 216
  30. 120
  31. motor
  32. an LED lamp
  33. red-yellow-black
  34. a motor
  35. 8.8
  36. the flow of charge
  37. thermistor
  38. 20
  39. 6
  40. limits the current

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