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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 270 · 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.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  2. 2.True or false: the ammeter is joined across a part. (a) True (b) False
  3. 3.📏 Which unit measures current? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
  4. 4.🧮 Two resistors in parallel give a total that is … (a) always zero (b) more than either one (c) their sum (d) less than either one
  5. 5.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  6. 6.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) smaller (c) bigger (d) zero
  7. 7.🔺 A current of 0.25 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.🔺 A current of 0.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.🌈 A resistor has the colour bands violet, green, red. What is its value (in ohms)?
  10. 10.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) the gold band (d) any band
  11. 11.⚡ A device works on 1.5 V and takes 2 A. What is its power (in watts)? =
  12. 12.What does a capacitor do? (a) beeps for an alarm (b) boosts a small signal (c) stores a little charge (d) glows using little power
  13. 13.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
  14. 14.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 4 hours. How many watt-hours (Wh) are saved?
  15. 15.🧮 A 3.5 V battery is joined to 3 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
  16. 16.💡 An LED is joined to a 9 V battery with no 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
  17. 17.⚡ 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
  18. 18.📏 How many kilo-ohms (kΩ) is 3200 Ω? =
  19. 19.🧩 Which component is a resistance knob? (a) potentiometer (b) transistor (c) resistor (d) thermistor
  20. 20.Which of these wastes electricity? (a) iron one shirt at a time (b) set the AC to 24 °C (c) switch off empty rooms (d) use LED lamps
  21. 21.🧩 Which component smooths a wobbly supply? (a) diode (b) fuse (c) motor (d) capacitor
  22. 22.🔺 A current of 3 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  23. 23.📏 Which unit measures resistance? (a) volt (V) (b) ampere (A) (c) watt (W) (d) ohm (Ω)
  24. 24.🔺 A 0.5 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  25. 25.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V + I (d) P = V × I
  26. 26.True or false: current is measured in amperes (A). (a) False (b) True
  27. 27.🔺 A 6.6 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
  28. 28.🧩 A capacitor in a circuit can … (a) measure heat (b) make light (c) spin a wheel (d) store charge briefly
  29. 29.What does a potentiometer do? (a) boosts a small signal (b) makes a beeping sound (c) stores a little charge (d) is a resistance knob
  30. 30.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
  31. 31.🔺 A current of 1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.True or false: the push of a cell is measured in ohms (Ω). (a) True (b) False
  33. 33.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
  34. 34.What does a fuse do? (a) makes things spin (b) senses how hot it is (c) blows if current is high (d) senses how bright it is
  35. 35.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.🔺 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
  37. 37.🔺 A 10 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
  38. 38.⚡ A 4.8 W device works on 24 V. What current does it take (in amperes)? =
  39. 39.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it does not light (c) it changes colour (d) it makes a sound
  40. 40.⚡ A 15 W device works on 5 V. What current does it take (in amperes)? =

Answer key

  1. 10
  2. False
  3. ampere (A)
  4. less than either one
  5. cathode (−)
  6. bigger
  7. 5
  8. 2
  9. 7500
  10. the one nearest an end
  11. 3
  12. stores a little charge
  13. 0.2
  14. 136
  15. 0.5
  16. may burn out
  17. energy used each second
  18. 3.2
  19. potentiometer
  20. iron one shirt at a time
  21. capacitor
  22. 9
  23. ohm (Ω)
  24. 0.25
  25. P = V × I
  26. True
  27. 20
  28. store charge briefly
  29. is a resistance knob
  30. 330
  31. 8
  32. False
  33. saves electricity
  34. blows if current is high
  35. 1
  36. V = I × R
  37. 20
  38. 0.2
  39. it does not light
  40. 3

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