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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 956 · 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 capacitor in a circuit can … (a) store charge briefly (b) measure heat (c) make light (d) spin a wheel
  2. 2.What does a fuse do? (a) blows if current is high (b) is a resistance knob (c) has coloured bands (d) stores a little charge
  3. 3.💡 A red LED uses 2 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  4. 4.🔺 A current of 1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  5. 5.🔺 A 30 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  6. 6.💡 Why does an LED need a resistor in series? (a) to store charge (b) to limit the current (c) to make it brighter (d) to change its colour
  7. 7.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V × R (c) I = V + R (d) I = V ÷ R
  8. 8.🌈 Which band is read first on a resistor? (a) any band (b) the gold band (c) the one nearest an end (d) the widest gap
  9. 9.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  10. 10.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
  11. 11.🔺 A current of 50 mA flows when 23.5 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.True or false: the ammeter measures voltage. (a) True (b) False
  13. 13.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) less than either one (d) more than either one
  14. 14.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an LED lamp (c) an oil lamp (d) a filament bulb
  15. 15.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a fuse (d) a motor
  16. 16.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) does not light (c) may burn out
  17. 17.🔺 A current of 50 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.True or false: the ammeter measures current. (a) True (b) False
  19. 19.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
  20. 20.🔺 A current of 0.2 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.True or false: to use LED lamps saves electricity. (a) True (b) False
  22. 22.🔺 A current of 2.5 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  23. 23.🔺 A current of 25 mA flows when 5.5 V is joined across a resistor. What is its resistance (in ohms)?
  24. 24.True or false: a transistor senses how hot it is. (a) False (b) True
  25. 25.💡 Does it save or waste electricity to set the AC to 24 °C? (a) saves electricity (b) wastes electricity
  26. 26.📏 How many milliamperes (mA) is 1.91 A?
  27. 27.🔺 A current of 20 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  28. 28.💡 Does it save or waste electricity to run fans in empty rooms? (a) wastes electricity (b) saves electricity
  29. 29.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
  30. 30.📏 How many ohms (Ω) is 2.3 kΩ?
  31. 31.⚡ 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
  32. 32.🧮 Resistors of 68 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
  33. 33.🧩 Which component is a resistance knob? (a) LED (b) motor (c) potentiometer (d) capacitor
  34. 34.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  35. 35.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
  36. 36.🌈 A resistor has the colour bands red, blue, orange. What is its value in kilo-ohms (kΩ)? =
  37. 37.True or false: a thermistor senses how hot it is. (a) False (b) True
  38. 38.🌈 A resistor has the colour bands yellow, brown, black. What is its value (in ohms)?
  39. 39.🔺 A current of 0.2 A flows through a 2 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) False (b) True

Answer key

  1. store charge briefly
  2. blows if current is high
  3. 700
  4. 12
  5. 1.5
  6. to limit the current
  7. I = V ÷ R
  8. the one nearest an end
  9. 345
  10. True
  11. 470
  12. False
  13. less than either one
  14. an LED lamp
  15. a motor
  16. lights up
  17. 200
  18. True
  19. saves electricity
  20. 1.2
  21. True
  22. 8
  23. 220
  24. False
  25. saves electricity
  26. 1910
  27. 8
  28. wastes electricity
  29. 1
  30. 2300
  31. energy used each second
  32. 538
  33. potentiometer
  34. 115
  35. True
  36. 26
  37. True
  38. 41
  39. 0.4
  40. True

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