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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 822 · 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.What does an LED do? (a) senses how hot it is (b) boosts a small signal (c) has coloured bands (d) glows using little power
  2. 2.🧩 Which component turns a fan or wheels? (a) diode (b) potentiometer (c) buzzer (d) motor
  3. 3.📏 Which unit measures how much a part resists? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
  4. 4.🔺 A current of 50 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
  5. 5.🔍 Which is the odd one out? (a) unplug idle chargers (b) use daylight to read (c) use old filament bulbs (d) close the fridge quickly
  6. 6.True or false: power is measured in ohms (Ω). (a) False (b) True
  7. 7.🌈 A resistor has the colour bands orange, black, black. What is its value (in ohms)?
  8. 8.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
  9. 9.📏 How many kilo-ohms (kΩ) is 1100 Ω? =
  10. 10.📏 Which unit measures power? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
  11. 11.🔺 A current of 1.5 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
  12. 12.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets smaller (d) gets bigger
  13. 13.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
  14. 14.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
  15. 15.🧮 Resistors of 220 Ω, 47 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
  16. 16.🔺 A current of 2.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
  17. 17.Which of these saves electricity? (a) leave the TV on standby (b) close the fridge quickly (c) leave fridge door open (d) use old filament bulbs
  18. 18.🌈 A resistor has the colour bands brown, yellow, red. What is its value (in ohms)?
  19. 19.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 50 % (c) 5 % (d) 25 %
  20. 20.🧾 A 500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
  21. 21.Which of these is measured in watts (W)? (a) the push of a cell (b) power (c) the flow of charge (d) voltage
  22. 22.📏 How many kilowatts (kW) is 2700 W? =
  23. 23.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 1000 (d) 10
  24. 24.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 22 Ω resistor? (a) red-orange-black (b) red-red-brown (c) orange-red-black (d) red-red-black
  25. 25.🔍 Which is the odd one out? (a) close the fridge quickly (b) use old filament bulbs (c) leave fridge door open (d) leave the TV on standby
  26. 26.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 watt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
  27. 27.🔺 A 6.25 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
  28. 28.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
  29. 29.⚡ A device works on 1.5 V and takes 1.5 A. What is its power (in watts)? =
  30. 30.True or false: to unplug idle chargers saves electricity. (a) True (b) False
  31. 31.💡 An LED is joined to a 9 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) may burn out (c) does not light
  32. 32.True or false: the ammeter measures voltage. (a) True (b) False
  33. 33.True or false: how much a part resists is measured in ohms (Ω). (a) False (b) True
  34. 34.What does a capacitor do? (a) senses how bright it is (b) smooths a wobbly supply (c) beeps for an alarm (d) lets current go one way
  35. 35.🔺 A current of 2.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  36. 36.🔺 A current of 50 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
  37. 37.⚡ A device works on 5 V and takes 1.5 A. What is its power (in watts)? =
  38. 38.📏 How many ohms (Ω) is 8.8 kΩ?
  39. 39.💡 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)?
  40. 40.🔍 Which is the odd one out? (a) leave fridge door open (b) iron one shirt at a time (c) leave the TV on standby (d) unplug idle chargers

Answer key

  1. glows using little power
  2. motor
  3. ohm (Ω)
  4. 20
  5. use old filament bulbs
  6. False
  7. 30
  8. 204
  9. 1.1
  10. watt (W)
  11. 10
  12. gets smaller
  13. 230
  14. 920
  15. 300
  16. 30
  17. close the fridge quickly
  18. 1400
  19. 5 %
  20. 2
  21. power
  22. 2.7
  23. 1000
  24. red-red-black
  25. close the fridge quickly
  26. 1 kilowatt-hour (kWh)
  27. 25
  28. False
  29. 2.25
  30. True
  31. may burn out
  32. False
  33. True
  34. smooths a wobbly supply
  35. 5
  36. 400
  37. 7.5
  38. 8800
  39. 5
  40. unplug idle chargers

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