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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 24 · 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 unit measures voltage? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
  2. 2.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  3. 3.🔺 A 50 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
  4. 4.💡 Does it save or waste electricity to close the fridge quickly? (a) wastes electricity (b) saves electricity
  5. 5.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 ampere (c) 1 watt (d) 1 kilowatt-hour (kWh)
  6. 6.📏 How many watts (W) is 4.2 kW?
  7. 7.🔺 A 30 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  8. 8.🔺 A 7.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  9. 9.📏 How many ohms (Ω) is 8.9 kΩ?
  10. 10.🌈 A resistor has the colour bands blue, grey, red. What is its value in kilo-ohms (kΩ)? =
  11. 11.🔺 A current of 1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
  12. 12.🔺 A current of 0.1 A flows when 0.3 V is joined across a resistor. What is its resistance (in ohms)?
  13. 13.🧩 Which part changes electrical energy into sound? (a) a diode (b) a capacitor (c) a resistor (d) a buzzer
  14. 14.⚡ 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
  15. 15.🔺 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
  16. 16.🧩 Which component turns a fan or wheels? (a) potentiometer (b) LED (c) diode (d) motor
  17. 17.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an oil lamp (d) an LED lamp
  18. 18.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
  19. 19.🌈 Which band is read first on a resistor? (a) the gold band (b) the one nearest an end (c) any band (d) the widest gap
  20. 20.🧮 A 2.2 V battery is joined to 10 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
  21. 21.🔺 A current of 3 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  22. 22.Which of these is measured in amperes (A)? (a) the flow of charge (b) how much a part resists (c) energy used each second (d) resistance
  23. 23.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  24. 24.Which of these is measured in watts (W)? (a) current (b) power (c) resistance (d) voltage
  25. 25.What does a thermistor do? (a) senses how hot it is (b) blows if current is high (c) makes things spin (d) makes a beeping sound
  26. 26.⚡ A device works on 12 V and takes 3 A. What is its power (in watts)? =
  27. 27.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
  28. 28.🧩 Which component boosts a small signal? (a) motor (b) fuse (c) buzzer (d) transistor
  29. 29.📏 How many amperes (A) is 390 mA? =
  30. 30.💡 An LED is joined to a 9 V battery through a 220 Ω 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
  31. 31.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
  32. 32.What does a transistor do? (a) smooths a wobbly supply (b) stores a little charge (c) limits the current (d) boosts a small signal
  33. 33.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets bigger (d) gets smaller
  34. 34.📏 Which unit measures current? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)
  35. 35.🔺 A current of 0.5 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  36. 36.True or false: resistance is measured in volts (V). (a) True (b) False
  37. 37.True or false: to run fans in empty rooms saves electricity. (a) True (b) False
  38. 38.True or false: the ammeter measures voltage. (a) True (b) False
  39. 39.⚡ A device works on 6 V and takes 0.2 A. What is its power (in watts)? =
  40. 40.📏 Which unit measures how much a part resists? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)

Answer key

  1. volt (V)
  2. 7.5
  3. 2.5
  4. saves electricity
  5. 1 kilowatt-hour (kWh)
  6. 4200
  7. 2
  8. 0.5
  9. 8900
  10. 6.8
  11. 3
  12. 3
  13. a buzzer
  14. energy used each second
  15. I = V ÷ R
  16. motor
  17. an LED lamp
  18. 0.2
  19. the one nearest an end
  20. 0.1
  21. 30
  22. the flow of charge
  23. 4
  24. power
  25. senses how hot it is
  26. 36
  27. True
  28. transistor
  29. 0.39
  30. does not light
  31. 12.5
  32. boosts a small signal
  33. gets smaller
  34. ampere (A)
  35. 10
  36. False
  37. False
  38. False
  39. 1.2
  40. ohm (Ω)

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