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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 251 · 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 green, green, red. What is its value in kilo-ohms (kΩ)? =
  2. 2.🔺 A 7.5 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
  3. 3.💡 An LED is joined to a 5 V battery through a 470 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) lights up (c) does not light
  4. 4.🔺 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
  5. 5.⚡ A device works on 24 V and takes 0.25 A. What is its power (in watts)? =
  6. 6.What does a transistor do? (a) turns a fan or wheels (b) beeps for an alarm (c) boosts a small signal (d) has coloured bands
  7. 7.📏 Which unit measures current? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
  8. 8.Which of these wastes electricity? (a) close the fridge quickly (b) set the AC to 24 °C (c) unplug idle chargers (d) leave the TV on standby
  9. 9.🧾 A 250 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
  10. 10.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  11. 11.🧩 Which component blows if current is high? (a) resistor (b) motor (c) fuse (d) thermistor
  12. 12.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
  13. 13.📏 Which unit measures resistance? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
  14. 14.🔺 An 8 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  15. 15.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  16. 16.🧩 A capacitor in a circuit can … (a) spin a wheel (b) measure heat (c) store charge briefly (d) make light
  17. 17.🔺 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
  18. 18.🧮 A 13 V battery is joined to 8 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
  19. 19.True or false: an LDR senses how bright it is. (a) True (b) False
  20. 20.🔺 A 0.5 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  21. 21.🔺 A current of 2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  22. 22.🌈 A resistor has the colour bands green, black, brown. What is its value (in ohms)?
  23. 23.🧾 A 500 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
  24. 24.🧩 Which component makes things spin? (a) transistor (b) potentiometer (c) resistor (d) motor
  25. 25.What does a potentiometer do? (a) is a resistance knob (b) senses how hot it is (c) glows using little power (d) blows if current is high
  26. 26.🔺 A current of 10 mA flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
  27. 27.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  28. 28.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🔺 A current of 50 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  30. 30.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
  31. 31.True or false: to leave the TV on standby wastes electricity. (a) False (b) True
  32. 32.🌈 In the resistor colour code, which number does black stand for?
  33. 33.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to change its colour (d) to store charge
  34. 34.🔺 An 11 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
  35. 35.🔺 An 18 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
  36. 36.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
  37. 37.💡 An LED is joined to a 6 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) may burn out (c) lights up
  38. 38.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an LED lamp (d) an oil lamp
  39. 39.🔺 A current of 0.1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🧾 A 1000 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =

Answer key

  1. 5.5
  2. 25
  3. lights up
  4. R = V ÷ I
  5. 6
  6. boosts a small signal
  7. ampere (A)
  8. leave the TV on standby
  9. 1.5
  10. 100
  11. fuse
  12. ammeter
  13. ohm (Ω)
  14. 1
  15. 5
  16. store charge briefly
  17. V = I × R
  18. 1
  19. True
  20. 0.25
  21. 16
  22. 500
  23. 4
  24. motor
  25. is a resistance knob
  26. 100
  27. anode (+)
  28. 4
  29. 5
  30. 1150
  31. True
  32. 0
  33. to limit the current
  34. 50
  35. 3
  36. True
  37. may burn out
  38. an LED lamp
  39. 1.5
  40. 6

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