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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 815 · 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.Which of these saves electricity? (a) run fans in empty rooms (b) use LED lamps (c) iron one shirt at a time (d) leave the TV on standby
  2. 2.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
  3. 3.🧾 Which lamp gives the same light for the least power? (a) a candle (b) a filament bulb (c) an oil lamp (d) an LED lamp
  4. 4.🔺 A current of 50 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
  5. 5.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
  6. 6.True or false: a transistor glows using little power. (a) False (b) True
  7. 7.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
  8. 8.🔺 A 1.25 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
  9. 9.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.🧮 A 20 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  11. 11.🔍 Which is the odd one out? (a) unplug idle chargers (b) iron one shirt at a time (c) use daylight to read (d) switch off empty rooms
  12. 12.🔺 A current of 0.5 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
  13. 13.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to limit the current (d) to store charge
  15. 15.🧩 Which component senses how bright it is? (a) LED (b) capacitor (c) transistor (d) LDR
  16. 16.True or false: power is measured in watts (W). (a) True (b) False
  17. 17.📏 How many milliamperes (mA) is 1.34 A?
  18. 18.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
  19. 19.⚡ 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
  20. 20.🔺 A current of 1 A flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
  21. 21.🔺 A current of 50 mA flows when 23.5 V is joined across a resistor. What is its resistance (in ohms)?
  22. 22.⚡ A device works on 5 V and takes 3 A. What is its power (in watts)? =
  23. 23.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I × R (c) V = R ÷ I (d) V = I ÷ R
  24. 24.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  25. 25.🔺 A current of 1 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  26. 26.💡 Does it save or waste electricity to use LED lamps? (a) saves electricity (b) wastes electricity
  27. 27.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = I ÷ V (d) P = V ÷ I
  28. 28.🔺 A current of 1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  29. 29.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 watt (c) 1 ampere (d) 1 volt
  30. 30.🔺 A current of 40 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  31. 31.True or false: the ammeter is joined in series. (a) True (b) False
  32. 32.📏 Which unit measures the flow of charge? (a) ohm (Ω) (b) volt (V) (c) ampere (A) (d) watt (W)
  33. 33.📏 How many milliamperes (mA) is 0.89 A?
  34. 34.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  35. 35.🔺 A current of 25 mA flows when 6.25 V is joined across a resistor. What is its resistance (in ohms)?
  36. 36.🧾 A family uses 100 units of electricity in a month and each unit costs ₹8. What is the bill (in ₹)?
  37. 37.🔺 A 36 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
  38. 38.True or false: to leave fridge door open wastes electricity. (a) True (b) False
  39. 39.🧾 A family uses 130 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
  40. 40.🧮 Resistors of 50 Ω, 10 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?

Answer key

  1. use LED lamps
  2. 920
  3. an LED lamp
  4. 150
  5. 3
  6. False
  7. less than either one
  8. 0.25
  9. 37.5
  10. 70
  11. iron one shirt at a time
  12. 2
  13. 2.4
  14. to limit the current
  15. LDR
  16. True
  17. 1340
  18. 2
  19. energy used each second
  20. 10
  21. 470
  22. 15
  23. V = I × R
  24. 8
  25. 20
  26. saves electricity
  27. P = V × I
  28. 6
  29. 1 kilowatt-hour (kWh)
  30. 4.8
  31. True
  32. ampere (A)
  33. 890
  34. 0.5
  35. 250
  36. 800
  37. 3
  38. True
  39. 520
  40. 110

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