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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 311 · 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 component makes a beeping sound? (a) buzzer (b) resistor (c) fuse (d) capacitor
  2. 2.🔺 A current of 0.1 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
  3. 3.🔺 A current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
  5. 5.⚡ A device works on 6 V and takes 0.2 A. What is its power (in watts)? =
  6. 6.Which of these saves electricity? (a) run fans in empty rooms (b) use old filament bulbs (c) set the AC to 24 °C (d) iron one shirt at a time
  7. 7.What does a thermistor do? (a) stores a little charge (b) makes things spin (c) senses how bright it is (d) senses how hot it is
  8. 8.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a motor (d) a fuse
  9. 9.🧮 Resistors of 220 Ω, 20 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
  10. 10.🔺 A current of 1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
  11. 11.🔺 A current of 40 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.⚡ 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
  13. 13.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
  14. 14.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  15. 15.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V × I (c) R = I ÷ V (d) R = V + I
  16. 16.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
  17. 17.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
  18. 18.Which of these is measured in volts (V)? (a) energy used each second (b) the push of a cell (c) power (d) resistance
  19. 19.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) less than either one (d) more than either one
  20. 20.🌈 In the resistor colour code, which number does yellow stand for?
  21. 21.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
  22. 22.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  23. 23.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) store charge briefly (d) measure heat
  24. 24.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
  25. 25.🔺 A current of 3 A flows when 24 V is joined across a resistor. What is its resistance (in ohms)?
  26. 26.🧩 Which component turns a fan or wheels? (a) transistor (b) potentiometer (c) diode (d) motor
  27. 27.True or false: an LED makes a beeping sound. (a) True (b) False
  28. 28.🔺 A current of 0.2 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
  29. 29.⚡ A 3 W device works on 6 V. What current does it take (in amperes)? =
  30. 30.⚡ A 5 W device works on 5 V. What current does it take (in amperes)? =
  31. 31.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
  32. 32.True or false: the voltmeter measures current. (a) True (b) False
  33. 33.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  34. 34.🔺 A current of 25 mA flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
  35. 35.💡 An LED is joined to a 3 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) does not light (c) may burn out
  36. 36.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) a bigger tank (c) the flow of water (d) the water pressure
  37. 37.💡 Does it save or waste electricity to unplug idle chargers? (a) saves electricity (b) wastes electricity
  38. 38.📏 How many ohms (Ω) is 6.8 kΩ?
  39. 39.🔺 A current of 0.2 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = I ÷ V (d) P = V + I

Answer key

  1. buzzer
  2. 8
  3. 5
  4. 1840
  5. 1.2
  6. set the AC to 24 °C
  7. senses how hot it is
  8. a motor
  9. 250
  10. 10
  11. 150
  12. energy used each second
  13. 1.5
  14. cathode (−)
  15. R = V ÷ I
  16. 255
  17. False
  18. the push of a cell
  19. less than either one
  20. 4
  21. wastes electricity
  22. 4
  23. store charge briefly
  24. 2.5
  25. 8
  26. motor
  27. False
  28. 4
  29. 0.5
  30. 1
  31. gets smaller
  32. False
  33. 235
  34. 500
  35. lights up
  36. a narrow pipe
  37. saves electricity
  38. 6800
  39. 4
  40. P = V × I

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