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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 708 · 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.📏 How many milliamperes (mA) is 0.79 A?
  2. 2.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V × I (c) R = V ÷ I (d) R = V + I
  3. 3.Which of these wastes electricity? (a) close the fridge quickly (b) iron one shirt at a time (c) use LED lamps (d) set the AC to 24 °C
  4. 4.💡 An LED is joined to a 6 V battery through a 1000 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) may burn out (c) lights up
  5. 5.What does a diode do? (a) is a resistance knob (b) turns a fan or wheels (c) lets current go one way (d) limits the current
  6. 6.🔺 A current of 2.5 A flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.🔺 A 0.8 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  8. 8.⚡ A device works on 1.5 V and takes 2 A. What is its power (in watts)? =
  9. 9.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  10. 10.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
  11. 11.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  12. 12.🌈 In the resistor colour code, which number does blue stand for?
  13. 13.🌈 A resistor has the colour bands brown, red, orange. What is its value in kilo-ohms (kΩ)? =
  14. 14.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  15. 15.🔺 A 1 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  16. 16.True or false: the flow of charge is measured in amperes (A). (a) True (b) False
  17. 17.🧩 Which component stores a little charge? (a) LED (b) diode (c) capacitor (d) resistor
  18. 18.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
  19. 19.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I × R (c) V = I ÷ R (d) V = R ÷ I
  20. 20.🔍 Which is the odd one out? (a) switch off empty rooms (b) unplug idle chargers (c) close the fridge quickly (d) use old filament bulbs
  21. 21.What does a motor do? (a) limits the current (b) stores a little charge (c) lets current go one way (d) turns a fan or wheels
  22. 22.True or false: the push of a cell is measured in ohms (Ω). (a) False (b) True
  23. 23.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 2.75 V supply. What current flows (in mA)?
  24. 24.💡 What happens if an LED is put in backwards? (a) it does not light (b) it changes colour (c) it makes a sound (d) it lights brighter
  25. 25.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
  26. 26.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 0 % (d) 5 %
  27. 27.🔺 A current of 1.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  28. 28.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets bigger (c) stays the same (d) gets smaller
  29. 29.🌈 A resistor has the colour bands white, red, brown. What is its value (in ohms)?
  30. 30.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  31. 31.What does an LDR do? (a) makes a beeping sound (b) has coloured bands (c) senses how bright it is (d) stores a little charge
  32. 32.🔍 Which is the odd one out? (a) use LED lamps (b) run fans in empty rooms (c) leave the TV on standby (d) leave fridge door open
  33. 33.🧮 A 33 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  34. 34.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a buzzer (c) a resistor (d) a diode
  35. 35.⚡ An 18 W device works on 6 V. What current does it take (in amperes)? =
  36. 36.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
  37. 37.Which of these wastes electricity? (a) close the fridge quickly (b) use old filament bulbs (c) use daylight to read (d) use LED lamps
  38. 38.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
  39. 39.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a resistor (c) a motor (d) an LED
  40. 40.What does a buzzer do? (a) smooths a wobbly supply (b) turns a fan or wheels (c) stores a little charge (d) beeps for an alarm

Answer key

  1. 790
  2. R = V ÷ I
  3. iron one shirt at a time
  4. lights up
  5. lets current go one way
  6. 4
  7. 0.1
  8. 3
  9. 400
  10. True
  11. 10
  12. 6
  13. 12
  14. 345
  15. 0.2
  16. True
  17. capacitor
  18. P = V × I
  19. V = I × R
  20. use old filament bulbs
  21. turns a fan or wheels
  22. False
  23. 5
  24. it does not light
  25. 0.15
  26. 5 %
  27. 18
  28. gets smaller
  29. 920
  30. anode (+)
  31. senses how bright it is
  32. use LED lamps
  33. 268
  34. a buzzer
  35. 3
  36. 20
  37. use old filament bulbs
  38. bigger
  39. a motor
  40. beeps for an alarm

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