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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 724 · 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.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V + R (c) I = V × R (d) I = R ÷ V
  2. 2.🔍 Which is the odd one out? (a) leave fridge door open (b) use daylight to read (c) use old filament bulbs (d) leave the TV on standby
  3. 3.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  4. 4.⚡ A 10 W device works on 5 V. What current does it take (in amperes)? =
  5. 5.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
  6. 6.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) gets bigger (d) stays the same
  7. 7.📏 Which unit measures current? (a) watt (W) (b) ampere (A) (c) ohm (Ω) (d) volt (V)
  8. 8.⚡ Which formula gives electric power? (a) P = V × I (b) P = I ÷ V (c) P = V + I (d) P = V ÷ I
  9. 9.🔺 A current of 40 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
  10. 10.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
  11. 11.🔺 A current of 0.5 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.📏 Which unit measures how much a part resists? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
  13. 13.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
  14. 14.🌈 A resistor has the colour bands red, white, red. What is its value (in ohms)?
  15. 15.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  16. 16.⚡ 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
  17. 17.🔺 A current of 20 mA flows when 4.4 V is joined across a resistor. What is its resistance (in ohms)?
  18. 18.🔍 Which is the odd one out? (a) leave fridge door open (b) iron one shirt at a time (c) run fans in empty rooms (d) switch off empty rooms
  19. 19.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
  20. 20.📏 In the water-pipe picture of a circuit, current is like … (a) the pipe colour (b) the flow of water (c) a narrow pipe (d) the water pressure
  21. 21.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
  22. 22.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1024 (b) 10 (c) 100 (d) 1000
  23. 23.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the water pressure (c) the flow of water (d) a bigger tank
  24. 24.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  25. 25.🧮 A 1.4 V battery is joined to 3 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
  26. 26.🌈 In the resistor colour code, which number does violet stand for?
  27. 27.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
  28. 28.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I × R (c) V = I + R (d) V = I ÷ R
  29. 29.📏 How many kilowatts (kW) is 4300 W? =
  30. 30.True or false: the flow of charge is measured in watts (W). (a) False (b) True
  31. 31.🧩 Which component smooths a wobbly supply? (a) motor (b) capacitor (c) thermistor (d) potentiometer
  32. 32.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  33. 33.True or false: an LED is a resistance knob. (a) True (b) False
  34. 34.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
  35. 35.What does a resistor do? (a) makes a beeping sound (b) beeps for an alarm (c) boosts a small signal (d) limits the current
  36. 36.🔍 Which is the odd one out? (a) run fans in empty rooms (b) close the fridge quickly (c) unplug idle chargers (d) switch off empty rooms
  37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 550 Ω resistor? (a) green-green-red (b) green-blue-brown (c) green-green-brown (d) green-green-black
  38. 38.💡 An LED is joined to a 9 V battery through a 330 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
  39. 39.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
  40. 40.🔺 A current of 25 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =

Answer key

  1. I = V ÷ R
  2. use daylight to read
  3. 20
  4. 2
  5. voltmeter
  6. gets smaller
  7. ampere (A)
  8. P = V × I
  9. 12
  10. 460
  11. 6
  12. ohm (Ω)
  13. 8
  14. 2900
  15. 1.2
  16. energy used each second
  17. 220
  18. switch off empty rooms
  19. ammeter
  20. the flow of water
  21. 357
  22. 1000
  23. a narrow pipe
  24. 500
  25. 0.2
  26. 7
  27. 5
  28. V = I × R
  29. 4.3
  30. False
  31. capacitor
  32. 9.4
  33. False
  34. cathode (−)
  35. limits the current
  36. run fans in empty rooms
  37. green-green-brown
  38. lights up
  39. 11.75
  40. 6.25

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