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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 295 · 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.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) zero (d) stay the same
  2. 2.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  3. 3.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  4. 4.🔺 A current of 0.25 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  5. 5.🔺 A current of 50 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  6. 6.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 6.5 V supply. What current flows (in mA)?
  7. 7.🧮 Four equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  8. 8.🔺 A current of 0.2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.📏 Which unit measures power? (a) ohm (Ω) (b) volt (V) (c) ampere (A) (d) watt (W)
  10. 10.Which of these is measured in amperes (A)? (a) how much a part resists (b) current (c) resistance (d) voltage
  11. 11.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
  12. 12.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a buzzer (c) a resistor (d) a diode
  13. 13.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V × I (c) R = V ÷ I (d) R = I ÷ V
  14. 14.True or false: to iron one shirt at a time saves electricity. (a) True (b) False
  15. 15.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
  16. 16.🔺 A current of 10 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  18. 18.💡 An LED is joined to a 5 V battery through a 1000 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) lights up (c) may burn out
  19. 19.🔺 A 2.2 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
  20. 20.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  21. 21.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to limit the current (d) to change its colour
  22. 22.🧩 Which component blows if current is high? (a) fuse (b) motor (c) LDR (d) capacitor
  23. 23.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) becomes zero (c) gets smaller (d) stays the same
  24. 24.🧾 A 50 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
  25. 25.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 0 % (d) 50 %
  26. 26.🔺 A 1.25 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  27. 27.🧩 A capacitor in a circuit can … (a) spin a wheel (b) measure heat (c) make light (d) store charge briefly
  28. 28.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) the colour of light (d) energy used each second
  29. 29.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
  30. 30.True or false: the ammeter measures current. (a) False (b) True
  31. 31.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
  32. 32.🔺 A current of 25 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  33. 33.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
  34. 34.True or false: the voltmeter measures current. (a) False (b) True
  35. 35.What does an LED do? (a) lets current go one way (b) smooths a wobbly supply (c) limits the current (d) glows using little power
  36. 36.🔺 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
  37. 37.True or false: the ammeter is joined across a part. (a) False (b) True
  38. 38.🧮 A 16 V battery is joined to 12 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
  39. 39.🔺 A current of 0.1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False

Answer key

  1. bigger
  2. 200
  3. 165
  4. 1.25
  5. 20
  6. 15
  7. 50
  8. 0.4
  9. watt (W)
  10. current
  11. saves electricity
  12. a buzzer
  13. R = V ÷ I
  14. False
  15. voltmeter
  16. 3.3
  17. cathode (−)
  18. lights up
  19. 10
  20. 230
  21. to limit the current
  22. fuse
  23. gets smaller
  24. 0.25
  25. 5 %
  26. 0.25
  27. store charge briefly
  28. energy used each second
  29. 3
  30. True
  31. 920
  32. 200
  33. 10
  34. False
  35. glows using little power
  36. I = V ÷ R
  37. False
  38. 1
  39. 0.6
  40. True

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