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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 127 · 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 red LED (it uses 2 V) is joined with a 200 Ω resistor to a 6 V supply. What current flows (in mA)?
  2. 2.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = R ÷ V (c) I = V × R (d) I = V + R
  3. 3.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
  4. 4.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) energy used each second (d) the colour of light
  5. 5.What does a potentiometer do? (a) smooths a wobbly supply (b) senses how hot it is (c) makes things spin (d) is a resistance knob
  6. 6.🧮 A 3.6 V battery is joined to 6 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
  7. 7.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  8. 8.🔺 A current of 0.5 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  9. 9.True or false: a motor turns a fan or wheels. (a) True (b) False
  10. 10.True or false: a potentiometer is a resistance knob. (a) False (b) True
  11. 11.🔺 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
  12. 12.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to change its colour (d) to limit the current
  13. 13.🔺 A current of 0.1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.🧩 Which part changes electrical energy into movement? (a) an LED (b) a motor (c) a resistor (d) a fuse
  15. 15.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) more than either one (c) always zero (d) their sum
  16. 16.Which of these saves electricity? (a) leave the TV on standby (b) iron one shirt at a time (c) use old filament bulbs (d) unplug idle chargers
  17. 17.🌈 In the resistor colour code, which number does brown stand for?
  18. 18.💡 An LED is joined to a 3 V battery through a 220 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.💡 What does LED stand for? (a) large electric dial (b) light energy dial (c) low energy device (d) light-emitting diode
  20. 20.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V ÷ I (d) P = V × I
  21. 21.🔺 A current of 1.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  22. 22.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
  23. 23.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a buzzer (d) a capacitor
  24. 24.Which of these wastes electricity? (a) close the fridge quickly (b) switch off empty rooms (c) use daylight to read (d) use old filament bulbs
  25. 25.True or false: power is measured in watts (W). (a) True (b) False
  26. 26.Which of these is measured in amperes (A)? (a) voltage (b) the push of a cell (c) resistance (d) the flow of charge
  27. 27.🧮 Resistors of 470 Ω, 150 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
  28. 28.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  29. 29.🔺 A 12.5 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
  30. 30.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
  31. 31.Which of these is measured in watts (W)? (a) energy used each second (b) the flow of charge (c) how much a part resists (d) the push of a cell
  32. 32.🌈 A resistor has the colour bands brown, yellow, orange. What is its value in kilo-ohms (kΩ)? =
  33. 33.📏 In the water-pipe picture of a circuit, current is like … (a) a narrow pipe (b) the flow of water (c) the pipe colour (d) the water pressure
  34. 34.🔺 A current of 50 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
  35. 35.⚡ A device works on 12 V and takes 0.5 A. What is its power (in watts)? =
  36. 36.⚡ A 1.25 W device works on 5 V. What current does it take (in amperes)? =
  37. 37.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  38. 38.📏 Which unit measures power? (a) ampere (A) (b) watt (W) (c) volt (V) (d) ohm (Ω)
  39. 39.🧮 A 0.7 V battery is joined to 4 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
  40. 40.True or false: to leave fridge door open wastes electricity. (a) True (b) False

Answer key

  1. 20
  2. I = V ÷ R
  3. saves electricity
  4. energy used each second
  5. is a resistance knob
  6. 0.2
  7. anode (+)
  8. 10
  9. True
  10. True
  11. R = V ÷ I
  12. to limit the current
  13. 1.5
  14. a motor
  15. less than either one
  16. unplug idle chargers
  17. 1
  18. lights up
  19. light-emitting diode
  20. P = V × I
  21. 12
  22. 102
  23. a buzzer
  24. use old filament bulbs
  25. True
  26. the flow of charge
  27. 840
  28. 10
  29. 50
  30. 2300
  31. energy used each second
  32. 14
  33. the flow of water
  34. 16.5
  35. 6
  36. 0.25
  37. 20
  38. watt (W)
  39. 0.1
  40. True

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