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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 123 · 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.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to limit the current (d) to make it brighter
  2. 2.🌈 Which band is read first on a resistor? (a) the widest gap (b) any band (c) the gold band (d) the one nearest an end
  3. 3.🌈 A resistor has the colour bands brown, white, red. What is its value in kilo-ohms (kΩ)? =
  4. 4.Which of these saves electricity? (a) close the fridge quickly (b) iron one shirt at a time (c) use old filament bulbs (d) run fans in empty rooms
  5. 5.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
  6. 6.🌈 In the resistor colour code, which number does brown stand for?
  7. 7.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
  8. 8.🔺 A current of 2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
  10. 10.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = R ÷ V (d) I = V ÷ R
  11. 11.True or false: an LED is a resistance knob. (a) False (b) True
  12. 12.🔺 A current of 0.25 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  13. 13.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 volt (c) 1 watt (d) 1 kilowatt-hour (kWh)
  14. 14.⚡ A 3 W device works on 6 V. What current does it take (in amperes)? =
  15. 15.🌈 A resistor has the colour bands grey, orange, orange. What is its value (in ohms)?
  16. 16.⚡ A device works on 5 V and takes 1.5 A. What is its power (in watts)? =
  17. 17.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a candle (c) a filament bulb (d) an oil lamp
  18. 18.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) a fuse (d) an LED
  19. 19.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
  20. 20.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  22. 22.🔺 A current of 10 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  23. 23.🔺 A 4.8 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  24. 24.🔺 A 2.5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  25. 25.🔺 A current of 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  26. 26.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
  27. 27.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) always zero (d) less than either one
  28. 28.🧮 A 33 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  29. 29.🧩 Which component is a resistance knob? (a) potentiometer (b) buzzer (c) thermistor (d) motor
  30. 30.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
  31. 31.What does a capacitor do? (a) smooths a wobbly supply (b) boosts a small signal (c) has coloured bands (d) glows using little power
  32. 32.True or false: the voltmeter measures voltage. (a) False (b) True
  33. 33.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
  34. 34.Which of these is measured in amperes (A)? (a) the flow of charge (b) voltage (c) energy used each second (d) the push of a cell
  35. 35.🔺 A current of 1 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  36. 36.🔺 A 2.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  37. 37.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
  38. 38.💡 Does it save or waste electricity to set the AC to 24 °C? (a) saves electricity (b) wastes electricity
  39. 39.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
  40. 40.🔍 Which is the odd one out? (a) use LED lamps (b) set the AC to 24 °C (c) close the fridge quickly (d) iron one shirt at a time

Answer key

  1. to limit the current
  2. the one nearest an end
  3. 1.9
  4. close the fridge quickly
  5. 4.5
  6. 1
  7. 0.6
  8. 30
  9. True
  10. I = V ÷ R
  11. False
  12. 1.5
  13. 1 kilowatt-hour (kWh)
  14. 0.5
  15. 83000
  16. 7.5
  17. an LED lamp
  18. a motor
  19. True
  20. 2.4
  21. 1.2
  22. 3.3
  23. 40
  24. 25
  25. 6
  26. 120
  27. less than either one
  28. 268
  29. potentiometer
  30. 68
  31. smooths a wobbly supply
  32. True
  33. False
  34. the flow of charge
  35. 20
  36. 0.5
  37. P = V × I
  38. saves electricity
  39. saves electricity
  40. iron one shirt at a time

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