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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 692 · 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 current of 25 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  2. 2.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a candle (c) a filament bulb (d) an oil lamp
  3. 3.🔺 A current of 0.25 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.What does a fuse do? (a) senses how bright it is (b) blows if current is high (c) smooths a wobbly supply (d) limits the current
  5. 5.🔺 An 8.8 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
  6. 6.🔺 A current of 0.25 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  7. 7.📏 How many ohms (Ω) is 2.9 kΩ?
  8. 8.🧮 Resistors of 20 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
  9. 9.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
  10. 10.True or false: an LED stores a little charge. (a) False (b) True
  11. 11.📏 How many milliamperes (mA) is 0.8 A?
  12. 12.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V + I (c) R = V × I (d) R = V ÷ I
  13. 13.🔺 A 5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
  14. 14.🧮 A 1.6 V battery is joined to 4 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
  15. 15.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
  16. 16.🌈 A resistor has the colour bands white, grey, brown. What is its value (in ohms)?
  17. 17.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) smaller (d) bigger
  18. 18.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  19. 19.💡 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?
  20. 20.🧩 Which component limits the current? (a) LED (b) buzzer (c) resistor (d) motor
  21. 21.🔺 An 18.8 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
  22. 22.🧩 Which component makes things spin? (a) buzzer (b) motor (c) diode (d) LDR
  23. 23.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water tank lid (b) the water pressure (c) the tap handle (d) the pipe colour
  24. 24.💡 An LED is joined to a 12 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) may burn out (c) does not light
  25. 25.🔺 A current of 0.5 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  26. 26.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a capacitor (c) a diode (d) a resistor
  27. 27.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  28. 28.📏 How many watts (W) is 3 kW?
  29. 29.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  30. 30.🌈 A resistor has the colour bands white, red, red. What is its value (in ohms)?
  31. 31.Which of these is measured in volts (V)? (a) how much a part resists (b) energy used each second (c) the flow of charge (d) voltage
  32. 32.True or false: to leave the TV on standby wastes electricity. (a) False (b) True
  33. 33.🔺 A 4.8 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  34. 34.💡 Does it save or waste electricity to iron one shirt at a time? (a) saves electricity (b) wastes electricity
  35. 35.⚡ 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
  36. 36.📏 Which unit measures the flow of charge? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
  37. 37.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V + I (d) P = V × I
  38. 38.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) always zero (d) less than either one
  39. 39.🔺 A 2.4 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
  40. 40.⚡ A device works on 9 V and takes 1 A. What is its power (in watts)? =

Answer key

  1. 10
  2. an LED lamp
  3. 0.5
  4. blows if current is high
  5. 40
  6. 1.5
  7. 2900
  8. 170
  9. 920
  10. False
  11. 800
  12. R = V ÷ I
  13. 50
  14. 0.1
  15. saves electricity
  16. 980
  17. bigger
  18. anode (+)
  19. 400
  20. resistor
  21. 40
  22. motor
  23. the water pressure
  24. may burn out
  25. 10
  26. a buzzer
  27. False
  28. 3000
  29. 100
  30. 9200
  31. voltage
  32. True
  33. 40
  34. wastes electricity
  35. energy used each second
  36. ampere (A)
  37. P = V × I
  38. less than either one
  39. 20
  40. 9

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