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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 340 · 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 0.3 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  2. 2.🔺 A current of 50 mA flows when 25 V is joined across a resistor. What is its resistance (in ohms)?
  3. 3.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
  4. 4.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 0 % (d) 5 %
  5. 5.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets bigger (c) gets smaller (d) becomes zero
  6. 6.🔺 A current of 2 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.⚡ Power tells us … (a) energy used each second (b) the colour of light (c) the size of a cell (d) the length of a wire
  8. 8.True or false: the ammeter measures current. (a) True (b) False
  9. 9.True or false: a transistor boosts a small signal. (a) False (b) True
  10. 10.💡 An LED is joined to a 9 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) lights up (c) does not light
  11. 11.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  12. 12.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  13. 13.True or false: to switch off empty rooms saves electricity. (a) False (b) True
  14. 14.📏 Which unit measures energy used each second? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
  15. 15.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = V + I (d) P = I ÷ V
  16. 16.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) more than either one (d) less than either one
  17. 17.🌈 A resistor has the colour bands violet, brown, black. What is its value (in ohms)?
  18. 18.📏 How many amperes (A) is 2550 mA? =
  19. 19.🧮 Resistors of 22 Ω, 150 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
  20. 20.🔺 A current of 0.2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  21. 21.🌈 A resistor has the colour bands grey, green, red. What is its value in kilo-ohms (kΩ)? =
  22. 22.🔺 A 15 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  23. 23.📏 How many milliamperes (mA) is 0.64 A?
  24. 24.True or false: a potentiometer is a resistance knob. (a) True (b) False
  25. 25.⚡ A device works on 5 V and takes 0.1 A. What is its power (in watts)? =
  26. 26.🔺 A current of 50 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
  27. 27.🧮 An 11 V battery is joined to 5 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
  28. 28.True or false: an LDR blows if current is high. (a) False (b) True
  29. 29.🧾 A family uses 40 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
  30. 30.Which of these wastes electricity? (a) leave the TV on standby (b) set the AC to 24 °C (c) unplug idle chargers (d) use LED lamps
  31. 31.🧩 Which component limits the current? (a) motor (b) resistor (c) LDR (d) LED
  32. 32.📏 How many milliamperes (mA) is 0.72 A?
  33. 33.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  34. 34.🧾 A family uses 70 units of electricity in a month and each unit costs ₹7. What is the bill (in ₹)?
  35. 35.🔺 A current of 0.1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.🧾 A family uses 30 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
  37. 37.True or false: an LED glows using little power. (a) False (b) True
  38. 38.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
  39. 39.True or false: voltage is measured in watts (W). (a) False (b) True
  40. 40.🌈 In the resistor colour code, which number does grey stand for?

Answer key

  1. 0.1
  2. 500
  3. 400
  4. 5 %
  5. gets smaller
  6. 24
  7. energy used each second
  8. True
  9. True
  10. may burn out
  11. 23.5
  12. 25
  13. True
  14. watt (W)
  15. P = V × I
  16. less than either one
  17. 71
  18. 2.55
  19. 322
  20. 2
  21. 8.5
  22. 1
  23. 640
  24. True
  25. 0.5
  26. 12.5
  27. 1
  28. False
  29. 160
  30. leave the TV on standby
  31. resistor
  32. 720
  33. 20
  34. 490
  35. 0.5
  36. 120
  37. True
  38. 4.4
  39. False
  40. 8

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