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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 271 · 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 resistor has the colour bands yellow, yellow, brown. What is its value (in ohms)?
  2. 2.🔺 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
  3. 3.🔺 A current of 3 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.📏 How many milliamperes (mA) is 2.59 A?
  5. 5.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  6. 6.True or false: to leave the TV on standby wastes electricity. (a) True (b) False
  7. 7.🧾 A 200 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
  8. 8.True or false: the ammeter is joined in series. (a) True (b) False
  9. 9.📏 Which unit measures energy used each second? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
  10. 10.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  11. 11.🧮 Three equal 75 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  12. 12.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a capacitor (c) a buzzer (d) a diode
  13. 13.💡 What happens if an LED is put in backwards? (a) it does not light (b) it lights brighter (c) it changes colour (d) it makes a sound
  14. 14.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  15. 15.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) their sum (d) less than either one
  16. 16.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = I ÷ V (d) R = V ÷ I
  17. 17.🧾 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?
  18. 18.🌈 In the resistor colour code, which number does green stand for?
  19. 19.🌈 A resistor has the colour bands white, green, orange. What is its value in kilo-ohms (kΩ)? =
  20. 20.📏 In the water-pipe picture of a circuit, resistance is like … (a) the flow of water (b) the water pressure (c) a bigger tank (d) a narrow pipe
  21. 21.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) zero (d) stay the same
  22. 22.🧮 A 68 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  23. 23.True or false: a motor turns a fan or wheels. (a) True (b) False
  24. 24.🧩 Which component turns a fan or wheels? (a) diode (b) buzzer (c) motor (d) transistor
  25. 25.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  26. 26.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
  27. 27.🔺 A 4.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  28. 28.🧩 A capacitor in a circuit can … (a) measure heat (b) spin a wheel (c) store charge briefly (d) make light
  29. 29.🧩 Which component smooths a wobbly supply? (a) LED (b) capacitor (c) transistor (d) potentiometer
  30. 30.🧮 Four equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  31. 31.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  32. 32.True or false: the voltmeter is joined in series. (a) False (b) True
  33. 33.True or false: an LDR senses how hot it is. (a) True (b) False
  34. 34.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
  35. 35.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 200 Ω resistor? (a) orange-red-brown (b) red-black-brown (c) red-black-black (d) red-black-red
  36. 36.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 100 (b) 10 (c) 1000 (d) 1024
  37. 37.📏 How many kilowatts (kW) is 1000 W? =
  38. 38.📏 How many amperes (A) is 2030 mA? =
  39. 39.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
  40. 40.🔍 Which is the odd one out? (a) close the fridge quickly (b) switch off empty rooms (c) use old filament bulbs (d) use LED lamps

Answer key

  1. 440
  2. I = V ÷ R
  3. 6
  4. 2590
  5. 20
  6. True
  7. 1
  8. True
  9. watt (W)
  10. 345
  11. 25
  12. a buzzer
  13. it does not light
  14. 150
  15. less than either one
  16. R = V ÷ I
  17. 68
  18. 5
  19. 95
  20. a narrow pipe
  21. bigger
  22. 78
  23. True
  24. motor
  25. 20
  26. False
  27. 1.5
  28. store charge briefly
  29. capacitor
  30. 50
  31. 10
  32. False
  33. False
  34. 1150
  35. red-black-brown
  36. 1000
  37. 1
  38. 2.03
  39. voltmeter
  40. use old filament bulbs

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