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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 312 · 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.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
  2. 2.📏 How many milliamperes (mA) is 0.7 A?
  3. 3.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a capacitor (c) a resistor (d) a diode
  4. 4.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  5. 5.🔺 A current of 50 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  6. 6.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  7. 7.🧾 A 2000 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
  8. 8.🔺 A current of 1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = R ÷ I (c) V = I + R (d) V = I × R
  10. 10.🔺 A current of 2 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  11. 11.🔍 Which is the odd one out? (a) run fans in empty rooms (b) leave fridge door open (c) leave the TV on standby (d) unplug idle chargers
  12. 12.True or false: a buzzer makes a beeping sound. (a) True (b) False
  13. 13.Which of these wastes electricity? (a) close the fridge quickly (b) use LED lamps (c) set the AC to 24 °C (d) leave the TV on standby
  14. 14.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
  15. 15.💡 An LED is joined to a 6 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) may burn out (c) does not light
  16. 16.🔺 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
  17. 17.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the length of a wire (d) the colour of light
  18. 18.🔺 A current of 3 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  20. 20.💡 Does it save or waste electricity to leave fridge door open? (a) wastes electricity (b) saves electricity
  21. 21.True or false: a resistor limits the current. (a) True (b) False
  22. 22.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
  23. 23.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
  24. 24.🔺 A 1.25 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  25. 25.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
  26. 26.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to make it brighter (d) to store charge
  27. 27.⚡ A 13.5 W device works on 9 V. What current does it take (in amperes)? =
  28. 28.What does a buzzer do? (a) beeps for an alarm (b) makes things spin (c) limits the current (d) stores a little charge
  29. 29.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  30. 30.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) zero (d) stay the same
  31. 31.🔺 A current of 0.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.🌈 Which band is read first on a resistor? (a) the widest gap (b) any band (c) the gold band (d) the one nearest an end
  33. 33.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) becomes zero (c) gets smaller (d) stays the same
  34. 34.🔺 A current of 25 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
  35. 35.🔺 A current of 50 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.True or false: to use old filament bulbs saves electricity. (a) False (b) True
  37. 37.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
  38. 38.True or false: the voltmeter measures voltage. (a) True (b) False
  39. 39.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) their sum (c) always zero (d) less than either one
  40. 40.📏 How many watts (W) is 2 kW?

Answer key

  1. False
  2. 700
  3. a buzzer
  4. 345
  5. 25
  6. 50
  7. 8
  8. 10
  9. V = I × R
  10. 3
  11. unplug idle chargers
  12. True
  13. leave the TV on standby
  14. 460
  15. lights up
  16. R = V ÷ I
  17. energy used each second
  18. 45
  19. 300
  20. wastes electricity
  21. True
  22. 300
  23. 2.5
  24. 0.25
  25. 5
  26. to limit the current
  27. 1.5
  28. beeps for an alarm
  29. 23.5
  30. bigger
  31. 5
  32. the one nearest an end
  33. gets smaller
  34. 100
  35. 5
  36. False
  37. 3
  38. True
  39. less than either one
  40. 2000

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