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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 743 · 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) False (b) True
  2. 2.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  3. 3.📏 How many ohms (Ω) is 0.4 kΩ?
  4. 4.🔺 A current of 0.2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  5. 5.True or false: the push of a cell is measured in volts (V). (a) False (b) True
  6. 6.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 0 % (c) 5 % (d) 50 %
  7. 7.True or false: a transistor is a resistance knob. (a) True (b) False
  8. 8.🔺 A current of 2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  9. 9.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
  10. 10.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  11. 11.🔺 A current of 50 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
  12. 12.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  13. 13.🧮 Resistors of 10 Ω, 220 Ω, 20 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
  14. 14.📏 In the water-pipe picture of a circuit, current is like … (a) a narrow pipe (b) the pipe colour (c) the water pressure (d) the flow of water
  15. 15.🔺 A 9 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
  16. 16.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it lights brighter (c) it makes a sound (d) it does not light
  17. 17.🧮 A 10 V battery is joined to 2 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
  18. 18.🔺 A 20 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
  19. 19.🔺 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
  20. 20.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 watt (c) 1 kilowatt-hour (kWh) (d) 1 volt
  21. 21.⚡ Power tells us … (a) the size of a cell (b) energy used each second (c) the colour of light (d) the length of a wire
  22. 22.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  23. 23.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = V × I (d) P = I ÷ V
  24. 24.True or false: an LDR makes a beeping sound. (a) True (b) False
  25. 25.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 5 V supply. What current flows (in mA)?
  26. 26.What does a fuse do? (a) blows if current is high (b) makes a beeping sound (c) smooths a wobbly supply (d) limits the current
  27. 27.🔺 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
  28. 28.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
  29. 29.🌈 A resistor has the colour bands red, violet, orange. What is its value in kilo-ohms (kΩ)? =
  30. 30.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) measure heat (d) store charge briefly
  31. 31.📏 Which unit measures the flow of charge? (a) volt (V) (b) ampere (A) (c) watt (W) (d) ohm (Ω)
  32. 32.⚡ A device works on 24 V and takes 0.5 A. What is its power (in watts)? =
  33. 33.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
  34. 34.💡 An LED is joined to a 3 V battery through a 220 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) lights up (b) does not light (c) may burn out
  35. 35.🧾 A 100 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
  36. 36.🧩 Which part changes electrical energy into sound? (a) a diode (b) a capacitor (c) a buzzer (d) a resistor
  37. 37.True or false: the flow of charge is measured in watts (W). (a) False (b) True
  38. 38.🔺 A 1 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
  39. 39.🧮 Resistors of 33 Ω, 150 Ω, 68 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
  40. 40.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)

Answer key

  1. False
  2. cathode (−)
  3. 400
  4. 20
  5. True
  6. 5 %
  7. False
  8. 30
  9. 1
  10. anode (+)
  11. 12.5
  12. 120
  13. 272
  14. the flow of water
  15. 1.5
  16. it does not light
  17. 1
  18. 50
  19. I = V ÷ R
  20. 1 kilowatt-hour (kWh)
  21. energy used each second
  22. 235
  23. P = V × I
  24. False
  25. 15
  26. blows if current is high
  27. R = V ÷ I
  28. wastes electricity
  29. 27
  30. store charge briefly
  31. ampere (A)
  32. 12
  33. 460
  34. does not light
  35. 0.6
  36. a buzzer
  37. False
  38. 0.25
  39. 581
  40. anode (+)

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