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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 225 · 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 red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
  2. 2.True or false: a capacitor stores a little charge. (a) True (b) False
  3. 3.🔺 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
  4. 4.True or false: a transistor limits the current. (a) False (b) True
  5. 5.🌈 In the resistor colour code, which number does red stand for?
  6. 6.📏 How many amperes (A) is 2130 mA? =
  7. 7.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 watt (c) 1 volt (d) 1 ampere
  8. 8.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V + I (c) P = V × I (d) P = V ÷ I
  9. 9.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = I + R (c) V = I ÷ R (d) V = R ÷ I
  10. 10.What does a resistor do? (a) makes a beeping sound (b) senses how hot it is (c) glows using little power (d) limits the current
  11. 11.🧾 A family uses 160 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
  12. 12.True or false: to set the AC to 24 °C wastes electricity. (a) False (b) True
  13. 13.📏 How many milliamperes (mA) is 2.4 A?
  14. 14.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) always zero (c) their sum (d) more than either one
  15. 15.🔺 A current of 10 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
  16. 16.🌈 A resistor has the colour bands violet, red, orange. What is its value (in ohms)?
  17. 17.True or false: on an LED, the leg by the flat edge is the anode (+). (a) False (b) True
  18. 18.📏 How many kilowatts (kW) is 1250 W? =
  19. 19.🔺 A current of 0.1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  20. 20.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  21. 21.🧮 A 2.2 V battery is joined to 3 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
  22. 22.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  23. 23.🌈 In the resistor colour code, which number does violet stand for?
  24. 24.📏 How many kilowatts (kW) is 2150 W? =
  25. 25.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a buzzer (d) a capacitor
  26. 26.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  27. 27.🌈 A resistor has the colour bands yellow, violet, red. What is its value (in ohms)?
  28. 28.🧾 A family uses 170 units of electricity in a month and each unit costs ₹8. What is the bill (in ₹)?
  29. 29.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it does not light (d) it changes colour
  30. 30.📏 How many watts (W) is 2.9 kW?
  31. 31.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V + R (c) I = V × R (d) I = V ÷ R
  32. 32.💡 Does it save or waste electricity to close the fridge quickly? (a) wastes electricity (b) saves electricity
  33. 33.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 50 % (d) 25 %
  34. 34.🔺 A current of 25 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  35. 35.🧮 A 47 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
  36. 36.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) smaller (d) zero
  37. 37.What does a fuse do? (a) blows if current is high (b) beeps for an alarm (c) senses how bright it is (d) stores a little charge
  38. 38.🧩 Which component beeps for an alarm? (a) thermistor (b) buzzer (c) fuse (d) resistor
  39. 39.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an LED lamp (d) an oil lamp
  40. 40.🔺 A 1.2 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =

Answer key

  1. 160
  2. True
  3. R = V ÷ I
  4. False
  5. 2
  6. 2.13
  7. 1 kilowatt-hour (kWh)
  8. P = V × I
  9. V = I × R
  10. limits the current
  11. 640
  12. False
  13. 2400
  14. less than either one
  15. 400
  16. 72000
  17. False
  18. 1.25
  19. 0.3
  20. 230
  21. 0.2
  22. False
  23. 7
  24. 2.15
  25. a buzzer
  26. 4
  27. 4700
  28. 1360
  29. it does not light
  30. 2900
  31. I = V ÷ R
  32. saves electricity
  33. 5 %
  34. 120
  35. 72
  36. bigger
  37. blows if current is high
  38. buzzer
  39. an LED lamp
  40. 0.1

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