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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 915 · 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 longer leg is the anode (+). (a) False (b) True
  2. 2.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) their sum (d) less than either one
  3. 3.🔺 A current of 1.5 A flows when 4.5 V is joined across a resistor. What is its resistance (in ohms)?
  4. 4.🧮 Resistors of 100 Ω, 47 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
  5. 5.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V + I (c) R = V × I (d) R = I ÷ V
  6. 6.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) may burn out (c) does not light
  7. 7.🌈 A resistor has the colour bands blue, blue, black. What is its value (in ohms)?
  8. 8.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  9. 9.🔺 A current of 0.25 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the gold band (c) any band (d) the widest gap
  11. 11.💡 Does it save or waste electricity to use LED lamps? (a) saves electricity (b) wastes electricity
  12. 12.🧮 A 220 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  13. 13.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.📏 How many watts (W) is 2.1 kW?
  15. 15.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the water pressure (c) the pipe colour (d) the water tank lid
  16. 16.🔺 A current of 3 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V ÷ I (d) P = V × I
  18. 18.💡 Does it save or waste electricity to use daylight to read? (a) saves electricity (b) wastes electricity
  19. 19.🔺 A 6.6 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
  20. 20.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
  22. 22.🧮 A 2 V battery is joined to 6 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
  23. 23.🧾 A family uses 50 units of electricity in a month and each unit costs ₹8. What is the bill (in ₹)?
  24. 24.What does an LED do? (a) has coloured bands (b) is a resistance knob (c) beeps for an alarm (d) glows using little power
  25. 25.🔺 A current of 0.2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  26. 26.🔺 A current of 10 mA flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
  27. 27.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 25 % (d) 0 %
  28. 28.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
  30. 30.🔺 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
  31. 31.Which of these wastes electricity? (a) use LED lamps (b) close the fridge quickly (c) use daylight to read (d) run fans in empty rooms
  32. 32.🧮 Four equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  33. 33.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) energy used each second (d) the colour of light
  34. 34.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
  35. 35.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) stay the same (d) zero
  36. 36.True or false: a buzzer beeps for an alarm. (a) False (b) True
  37. 37.🌈 In the resistor colour code, which number does brown stand for?
  38. 38.⚡ A device works on 12 V and takes 1.5 A. What is its power (in watts)? =
  39. 39.What does a diode do? (a) beeps for an alarm (b) limits the current (c) lets current go one way (d) senses how bright it is
  40. 40.What does a capacitor do? (a) boosts a small signal (b) turns a fan or wheels (c) lets current go one way (d) smooths a wobbly supply

Answer key

  1. True
  2. less than either one
  3. 3
  4. 157
  5. R = V ÷ I
  6. may burn out
  7. 66
  8. anode (+)
  9. 3.75
  10. the one nearest an end
  11. saves electricity
  12. 330
  13. 20
  14. 2100
  15. the water pressure
  16. 45
  17. P = V × I
  18. saves electricity
  19. 20
  20. 60
  21. 345
  22. 0.25
  23. 400
  24. glows using little power
  25. 3
  26. 100
  27. 5 %
  28. 9.4
  29. 2.5
  30. V = I × R
  31. run fans in empty rooms
  32. 10
  33. energy used each second
  34. 200
  35. bigger
  36. True
  37. 1
  38. 18
  39. lets current go one way
  40. smooths a wobbly supply

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