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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 672 · 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.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = I ÷ V (c) R = V ÷ I (d) R = V × I
  2. 2.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 60 (c) 100 (d) 1000
  3. 3.🧮 A 1.1 V battery is joined to 5 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
  4. 4.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
  5. 5.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a buzzer (d) a capacitor
  6. 6.🔺 A current of 0.1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
  8. 8.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.📏 Which unit measures voltage? (a) ampere (A) (b) watt (W) (c) volt (V) (d) ohm (Ω)
  10. 10.🔺 A 20 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  11. 11.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
  12. 12.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
  13. 13.🔺 A 3 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  14. 14.🔺 A 10 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
  15. 15.🌈 A resistor has the colour bands grey, blue, red. What is its value in kilo-ohms (kΩ)? =
  16. 16.What does a thermistor do? (a) blows if current is high (b) makes a beeping sound (c) makes things spin (d) senses how hot it is
  17. 17.🌈 A resistor has the colour bands orange, violet, yellow. What is its value in kilo-ohms (kΩ)? =
  18. 18.🧩 Which component senses how hot it is? (a) resistor (b) thermistor (c) motor (d) capacitor
  19. 19.📏 In the water-pipe picture of a circuit, resistance is like … (a) the flow of water (b) a narrow pipe (c) a bigger tank (d) the water pressure
  20. 20.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 kilowatt-hour (kWh) (c) 1 volt (d) 1 watt
  21. 21.🌈 A resistor has the colour bands brown, yellow, red. What is its value (in ohms)?
  22. 22.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  23. 23.🧩 Which component is a resistance knob? (a) buzzer (b) capacitor (c) potentiometer (d) LED
  24. 24.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  25. 25.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
  26. 26.What does a potentiometer do? (a) blows if current is high (b) glows using little power (c) stores a little charge (d) is a resistance knob
  27. 27.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  28. 28.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 25 % (c) 0 % (d) 50 %
  29. 29.True or false: to leave fridge door open saves electricity. (a) False (b) True
  30. 30.What does an LDR do? (a) senses how bright it is (b) glows using little power (c) stores a little charge (d) blows if current is high
  31. 31.🧮 Four equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  32. 32.Which of these wastes electricity? (a) leave the TV on standby (b) use daylight to read (c) switch off empty rooms (d) close the fridge quickly
  33. 33.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) stay the same (d) smaller
  34. 34.🔺 A current of 0.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  36. 36.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
  37. 37.🔺 A current of 25 mA flows when 11.75 V is joined across a resistor. What is its resistance (in ohms)?
  38. 38.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
  39. 39.🔺 A current of 1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) less than either one (d) always zero

Answer key

  1. R = V ÷ I
  2. 1000
  3. 0.1
  4. 10
  5. a buzzer
  6. 0.8
  7. 20
  8. 2.5
  9. volt (V)
  10. 2.5
  11. 115
  12. 920
  13. 0.2
  14. 20
  15. 8.6
  16. senses how hot it is
  17. 370
  18. thermistor
  19. a narrow pipe
  20. 1 kilowatt-hour (kWh)
  21. 1400
  22. 5
  23. potentiometer
  24. False
  25. True
  26. is a resistance knob
  27. 10
  28. 5 %
  29. False
  30. senses how bright it is
  31. 10
  32. leave the TV on standby
  33. bigger
  34. 5
  35. 10
  36. 10
  37. 470
  38. 0.25
  39. 8
  40. less than either one

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