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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 714 · 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 50 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  2. 2.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
  3. 3.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
  4. 4.📏 Which unit measures current? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
  5. 5.🧩 Which component senses how hot it is? (a) thermistor (b) motor (c) resistor (d) LED
  6. 6.True or false: to leave fridge door open wastes electricity. (a) True (b) False
  7. 7.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 3 V supply. What current flows (in mA)?
  8. 8.💡 Does it save or waste electricity to run fans in empty rooms? (a) wastes electricity (b) saves electricity
  9. 9.💡 What happens if an LED is put in backwards? (a) it does not light (b) it lights brighter (c) it makes a sound (d) it changes colour
  10. 10.Which of these is measured in watts (W)? (a) resistance (b) how much a part resists (c) the flow of charge (d) power
  11. 11.🔺 A current of 2.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  12. 12.💡 What does LED stand for? (a) light energy dial (b) low energy device (c) large electric dial (d) light-emitting diode
  13. 13.🧩 A capacitor in a circuit can … (a) spin a wheel (b) store charge briefly (c) measure heat (d) make light
  14. 14.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 50 % (d) 25 %
  15. 15.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to store charge (c) to change its colour (d) to make it brighter
  16. 16.True or false: the voltmeter measures current. (a) True (b) False
  17. 17.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = R ÷ I (c) V = I ÷ R (d) V = I + R
  18. 18.Which of these is measured in amperes (A)? (a) current (b) how much a part resists (c) resistance (d) power
  19. 19.True or false: the voltmeter is joined across a part. (a) False (b) True
  20. 20.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  21. 21.🔺 A 3.75 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  22. 22.True or false: the ammeter measures current. (a) True (b) False
  23. 23.💡 Does it save or waste electricity to use daylight to read? (a) saves electricity (b) wastes electricity
  24. 24.True or false: the voltmeter measures voltage. (a) True (b) False
  25. 25.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 57 Ω resistor? (a) violet-green-black (b) green-violet-black (c) green-violet-brown (d) blue-violet-black
  26. 26.🔺 A current of 0.1 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
  27. 27.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  28. 28.True or false: the voltmeter is joined in series. (a) False (b) True
  29. 29.🧾 A family uses 30 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
  30. 30.🧮 Resistors of 50 Ω, 22 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
  31. 31.Which of these saves electricity? (a) use old filament bulbs (b) iron one shirt at a time (c) leave fridge door open (d) use LED lamps
  32. 32.What does a thermistor do? (a) lets current go one way (b) is a resistance knob (c) makes things spin (d) senses how hot it is
  33. 33.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
  34. 34.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.Which of these is measured in ohms (Ω)? (a) the flow of charge (b) how much a part resists (c) the push of a cell (d) energy used each second
  36. 36.🔺 A 12.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  37. 37.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) less than either one (d) more than either one
  38. 38.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 630 Ω resistor? (a) blue-orange-red (b) orange-blue-brown (c) blue-orange-brown (d) blue-orange-black
  39. 39.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  40. 40.🧩 Which component limits the current? (a) resistor (b) buzzer (c) capacitor (d) fuse

Answer key

  1. 100
  2. lights up
  3. False
  4. ampere (A)
  5. thermistor
  6. True
  7. 5
  8. wastes electricity
  9. it does not light
  10. power
  11. 50
  12. light-emitting diode
  13. store charge briefly
  14. 5 %
  15. to limit the current
  16. False
  17. V = I × R
  18. current
  19. True
  20. 100
  21. 0.25
  22. True
  23. saves electricity
  24. True
  25. green-violet-black
  26. 10
  27. 100
  28. False
  29. 120
  30. 119
  31. use LED lamps
  32. senses how hot it is
  33. voltmeter
  34. 1
  35. how much a part resists
  36. 2.5
  37. less than either one
  38. blue-orange-brown
  39. cathode (−)
  40. resistor

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