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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 845 · 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.🧾 Which lamp gives the same light for the least power? (a) a candle (b) a filament bulb (c) an LED lamp (d) an oil lamp
  2. 2.🔺 A 5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  3. 3.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V × I (c) R = V ÷ I (d) R = V + I
  4. 4.True or false: to leave the TV on standby wastes electricity. (a) True (b) False
  5. 5.What does an LDR do? (a) senses how hot it is (b) smooths a wobbly supply (c) makes things spin (d) senses how bright it is
  6. 6.🧮 A 10 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)?
  7. 7.⚡ A 0.15 W device works on 1.5 V. What current does it take (in amperes)? =
  8. 8.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 20 Ω resistor? (a) orange-red-black (b) red-black-brown (c) orange-black-black (d) red-black-black
  10. 10.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it does not light (c) it lights brighter (d) it makes a sound
  11. 11.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  12. 12.🧩 Which component lets current go one way? (a) thermistor (b) diode (c) capacitor (d) LDR
  13. 13.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  14. 14.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  15. 15.Which of these is measured in ohms (Ω)? (a) power (b) how much a part resists (c) the push of a cell (d) current
  16. 16.🔺 A current of 3 A flows when 36 V is joined across a resistor. What is its resistance (in ohms)?
  17. 17.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 ampere (c) 1 volt (d) 1 kilowatt-hour (kWh)
  18. 18.True or false: the voltmeter measures voltage. (a) False (b) True
  19. 19.Which of these saves electricity? (a) leave fridge door open (b) run fans in empty rooms (c) use old filament bulbs (d) set the AC to 24 °C
  20. 20.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 2.75 V supply. What current flows (in mA)?
  21. 21.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  22. 22.⚡ A 6 W device works on 24 V. What current does it take (in amperes)? =
  23. 23.🔺 A 5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  24. 24.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = R ÷ I (d) V = I × R
  25. 25.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 930 Ω resistor? (a) white-orange-brown (b) white-orange-red (c) white-orange-black (d) orange-white-brown
  26. 26.True or false: to close the fridge quickly wastes electricity. (a) True (b) False
  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.🔺 A current of 1.5 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  29. 29.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to limit the current (d) to store charge
  30. 30.🔺 A current of 0.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  31. 31.📏 Voltmeter or ammeter: which one is joined in series? (a) ammeter (b) voltmeter
  32. 32.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
  33. 33.🔺 A current of 2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  34. 34.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
  35. 35.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets bigger (c) stays the same (d) gets smaller
  36. 36.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the water tank lid (c) the pipe colour (d) the water pressure
  37. 37.🔺 A 30 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  38. 38.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  39. 39.What does a resistor do? (a) smooths a wobbly supply (b) boosts a small signal (c) has coloured bands (d) stores a little charge
  40. 40.True or false: an LDR senses how bright it is. (a) False (b) True

Answer key

  1. an LED lamp
  2. 0.5
  3. R = V ÷ I
  4. True
  5. senses how bright it is
  6. 245
  7. 0.1
  8. 1
  9. red-black-black
  10. it does not light
  11. 1840
  12. diode
  13. 10
  14. anode (+)
  15. how much a part resists
  16. 12
  17. 1 kilowatt-hour (kWh)
  18. True
  19. set the AC to 24 °C
  20. 5
  21. anode (+)
  22. 0.25
  23. 50
  24. V = I × R
  25. white-orange-brown
  26. False
  27. P = V × I
  28. 2
  29. to limit the current
  30. 10
  31. ammeter
  32. 5
  33. 8
  34. 238
  35. gets smaller
  36. the water pressure
  37. 3
  38. 15
  39. has coloured bands
  40. True

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