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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 165 · 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.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = I ÷ V (c) R = V × I (d) R = V + I
  2. 2.What does an LED do? (a) makes things spin (b) makes a beeping sound (c) glows using little power (d) turns a fan or wheels
  3. 3.💡 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
  4. 4.💡 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?
  5. 5.🔍 Which is the odd one out? (a) unplug idle chargers (b) close the fridge quickly (c) iron one shirt at a time (d) switch off empty rooms
  6. 6.🔺 A 5.5 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
  7. 7.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
  8. 8.🔺 A 4 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
  9. 9.🔺 A current of 2.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.🔺 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
  11. 11.🔺 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
  12. 12.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
  13. 13.What does a buzzer do? (a) blows if current is high (b) stores a little charge (c) senses how hot it is (d) makes a beeping sound
  14. 14.🔺 A current of 25 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
  15. 15.🧾 A family uses 180 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
  16. 16.Which of these is measured in amperes (A)? (a) the push of a cell (b) voltage (c) the flow of charge (d) resistance
  17. 17.🔺 A current of 20 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 280 Ω resistor? (a) grey-red-brown (b) red-grey-black (c) red-grey-brown (d) red-grey-red
  19. 19.Which of these saves electricity? (a) iron one shirt at a time (b) leave the TV on standby (c) leave fridge door open (d) use daylight to read
  20. 20.🧮 Resistors of 470 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
  21. 21.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) energy used each second (d) the length of a wire
  22. 22.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
  23. 23.🧾 A family uses 100 units of electricity in a month and each unit costs ₹7. What is the bill (in ₹)?
  24. 24.🔺 A current of 2 A flows when 16 V is joined across a resistor. What is its resistance (in ohms)?
  25. 25.What does a thermistor do? (a) lets current go one way (b) glows using little power (c) senses how hot it is (d) turns a fan or wheels
  26. 26.🔺 A current of 50 mA flows when 16.5 V is joined across a resistor. What is its resistance (in ohms)?
  27. 27.🔺 A current of 3 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  28. 28.Which of these is measured in volts (V)? (a) resistance (b) current (c) voltage (d) how much a part resists
  29. 29.💡 Does it save or waste electricity to close the fridge quickly? (a) saves electricity (b) wastes electricity
  30. 30.⚡ A 36 W device works on 12 V. What current does it take (in amperes)? =
  31. 31.🔺 A 5 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  32. 32.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1024 (b) 1000 (c) 100 (d) 10
  33. 33.💡 What happens if an LED is put in backwards? (a) it does not light (b) it changes colour (c) it lights brighter (d) it makes a sound
  34. 34.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a diode (c) a resistor (d) a buzzer
  35. 35.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  36. 36.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 140 Ω resistor? (a) brown-yellow-red (b) brown-yellow-brown (c) brown-yellow-black (d) yellow-brown-brown
  37. 37.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
  38. 38.⚡ A 6 W device works on 12 V. What current does it take (in amperes)? =
  39. 39.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 ampere (d) 1 watt
  40. 40.🔺 A 6 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =

Answer key

  1. R = V ÷ I
  2. glows using little power
  3. to limit the current
  4. 400
  5. iron one shirt at a time
  6. 25
  7. 2.4
  8. 0.5
  9. 12.5
  10. gets smaller
  11. I = V ÷ R
  12. 0.5
  13. makes a beeping sound
  14. 300
  15. 720
  16. the flow of charge
  17. 400
  18. red-grey-brown
  19. use daylight to read
  20. 517
  21. energy used each second
  22. True
  23. 700
  24. 8
  25. senses how hot it is
  26. 330
  27. 5
  28. voltage
  29. saves electricity
  30. 3
  31. 0.25
  32. 1000
  33. it does not light
  34. a buzzer
  35. 230
  36. brown-yellow-brown
  37. wastes electricity
  38. 0.5
  39. 1 kilowatt-hour (kWh)
  40. 0.5

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