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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 878 · 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 part changes electrical energy into movement? (a) a fuse (b) a resistor (c) an LED (d) a motor
  2. 2.💡 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) does not light (c) lights up
  3. 3.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) smaller (d) stay the same
  4. 4.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 10 (b) 1000 (c) 100 (d) 1024
  5. 5.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
  6. 6.⚡ A 2.25 W device works on 9 V. What current does it take (in amperes)? =
  7. 7.🧩 Which component senses how bright it is? (a) resistor (b) fuse (c) LDR (d) motor
  8. 8.True or false: an LDR is a resistance knob. (a) False (b) True
  9. 9.True or false: voltage is measured in ohms (Ω). (a) True (b) False
  10. 10.🔺 A current of 1.5 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
  11. 11.🧩 Which component boosts a small signal? (a) potentiometer (b) transistor (c) LDR (d) fuse
  12. 12.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
  13. 13.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
  14. 14.📏 How many amperes (A) is 880 mA? =
  15. 15.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  16. 16.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 10 (c) 1000 (d) 100
  17. 17.🔺 A current of 50 mA flows when 23.5 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.🔺 A 12 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
  19. 19.📏 Which unit measures the flow of charge? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
  20. 20.⚡ A 0.75 W device works on 1.5 V. What current does it take (in amperes)? =
  21. 21.Which of these saves electricity? (a) leave the TV on standby (b) iron one shirt at a time (c) use daylight to read (d) leave fridge door open
  22. 22.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
  23. 23.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) energy used each second (d) the size of a cell
  24. 24.True or false: the voltmeter measures voltage. (a) True (b) False
  25. 25.🔺 A 2 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
  26. 26.🔺 A current of 1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
  27. 27.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
  28. 28.💡 An LED is joined to a 9 V battery through a 1000 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) may burn out (c) lights up
  29. 29.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
  30. 30.🔺 A current of 0.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
  31. 31.⚡ A device works on 5 V and takes 1.5 A. What is its power (in watts)? =
  32. 32.True or false: the ammeter is joined across a part. (a) False (b) True
  33. 33.Which of these wastes electricity? (a) set the AC to 24 °C (b) use old filament bulbs (c) unplug idle chargers (d) use LED lamps
  34. 34.True or false: a thermistor senses how hot it is. (a) True (b) False
  35. 35.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a filament bulb (c) a candle (d) an oil lamp
  36. 36.🔺 A current of 1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  37. 37.📏 How many kilo-ohms (kΩ) is 3300 Ω? =
  38. 38.🧩 Which component makes a beeping sound? (a) LDR (b) buzzer (c) diode (d) LED
  39. 39.🔺 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
  40. 40.🔺 A 7.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?

Answer key

  1. a motor
  2. may burn out
  3. bigger
  4. 1000
  5. cathode (−)
  6. 0.25
  7. LDR
  8. False
  9. False
  10. 20
  11. transistor
  12. 0.15
  13. True
  14. 0.88
  15. 235
  16. 1000
  17. 470
  18. 3
  19. ampere (A)
  20. 0.5
  21. use daylight to read
  22. 2300
  23. energy used each second
  24. True
  25. 1
  26. 4
  27. 20
  28. lights up
  29. 0.375
  30. 10
  31. 7.5
  32. False
  33. use old filament bulbs
  34. True
  35. an LED lamp
  36. 2
  37. 3.3
  38. buzzer
  39. I = V ÷ R
  40. 50

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