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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 50 · 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 current of 1.5 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
  2. 2.🔺 A current of 40 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  3. 3.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to store charge (d) to change its colour
  4. 4.🔺 A 30 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  5. 5.🌈 A resistor has the colour bands blue, green, red. What is its value in kilo-ohms (kΩ)? =
  6. 6.🔺 A current of 25 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.🔺 A current of 2.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.Which of these wastes electricity? (a) close the fridge quickly (b) leave the TV on standby (c) use daylight to read (d) use LED lamps
  9. 9.⚡ Power tells us … (a) the length of a wire (b) the colour of light (c) the size of a cell (d) energy used each second
  10. 10.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
  11. 11.📏 Which unit measures how much a part resists? (a) volt (V) (b) ampere (A) (c) watt (W) (d) ohm (Ω)
  12. 12.🧾 A 100 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
  13. 13.🔺 A current of 0.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  15. 15.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  16. 16.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.🔺 A current of 2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  18. 18.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
  19. 19.🧮 Resistors of 330 Ω, 330 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
  20. 20.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) zero (d) stay the same
  21. 21.⚡ A device works on 9 V and takes 1.5 A. What is its power (in watts)? =
  22. 22.🌈 A resistor has the colour bands brown, yellow, red. What is its value (in ohms)?
  23. 23.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a diode (c) a resistor (d) a buzzer
  24. 24.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
  25. 25.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = R ÷ V (d) I = V ÷ R
  26. 26.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I + R (c) V = I ÷ R (d) V = I × R
  27. 27.True or false: to close the fridge quickly wastes electricity. (a) False (b) True
  28. 28.🧩 Which component stores a little charge? (a) LDR (b) capacitor (c) fuse (d) buzzer
  29. 29.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
  30. 30.🔺 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
  31. 31.🌈 In the resistor colour code, which number does yellow stand for?
  32. 32.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 200 Ω resistor? (a) red-black-black (b) orange-red-brown (c) red-black-brown (d) red-black-red
  33. 33.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  34. 34.🌈 A resistor has the colour bands green, green, red. What is its value in kilo-ohms (kΩ)? =
  35. 35.📏 How many kilowatts (kW) is 150 W? =
  36. 36.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  37. 37.🔺 A current of 0.2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  38. 38.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
  39. 39.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets smaller (d) gets bigger
  40. 40.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) less than either one (d) more than either one

Answer key

  1. 20
  2. 16
  3. to limit the current
  4. 2
  5. 6.5
  6. 100
  7. 20
  8. leave the TV on standby
  9. energy used each second
  10. 0.2
  11. ohm (Ω)
  12. 0.4
  13. 2
  14. anode (+)
  15. 20
  16. 37.5
  17. 6
  18. True
  19. 693
  20. bigger
  21. 13.5
  22. 1400
  23. a buzzer
  24. ammeter
  25. I = V ÷ R
  26. V = I × R
  27. False
  28. capacitor
  29. 1150
  30. R = V ÷ I
  31. 4
  32. red-black-brown
  33. anode (+)
  34. 5.5
  35. 0.15
  36. 10
  37. 0.4
  38. 0.375
  39. gets smaller
  40. less than either one

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