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Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 38 · 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.📏 How many watts (W) is 4.5 kW?
  2. 2.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V + I (c) P = V × I (d) P = V ÷ I
  3. 3.🔺 A current of 2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
  4. 4.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?
  5. 5.🔺 A 22.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
  6. 6.🔺 A current of 0.25 A flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
  7. 7.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 ampere (c) 1 kilowatt-hour (kWh) (d) 1 watt
  8. 8.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
  9. 9.🌈 A resistor has the colour bands white, yellow, red. What is its value (in ohms)?
  10. 10.Which of these is measured in ohms (Ω)? (a) current (b) how much a part resists (c) energy used each second (d) the push of a cell
  11. 11.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a buzzer (d) a capacitor
  12. 12.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  13. 13.🔺 A current of 0.25 A flows when 1.25 V is joined across a resistor. What is its resistance (in ohms)?
  14. 14.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 5 % (d) 0 %
  15. 15.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) an oil lamp (c) a candle (d) a filament bulb
  16. 16.🧩 Which component glows using little power? (a) thermistor (b) LED (c) buzzer (d) resistor
  17. 17.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
  18. 18.🌈 A resistor has the colour bands grey, violet, red. What is its value in kilo-ohms (kΩ)? =
  19. 19.💡 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) does not light (b) may burn out (c) lights up
  20. 20.What does an LDR do? (a) senses how bright it is (b) stores a little charge (c) blows if current is high (d) beeps for an alarm
  21. 21.🌈 In the resistor colour code, which number does grey stand for?
  22. 22.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
  23. 23.🔺 A current of 50 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
  24. 24.🔺 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
  25. 25.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
  26. 26.🌈 A resistor has the colour bands yellow, black, red. What is its value (in ohms)?
  27. 27.🔺 A 5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
  28. 28.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the flow of water (c) a bigger tank (d) the water pressure
  29. 29.📏 How many amperes (A) is 2680 mA? =
  30. 30.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
  31. 31.🧩 Which component beeps for an alarm? (a) resistor (b) diode (c) buzzer (d) potentiometer
  32. 32.🔺 A current of 20 mA flows when 4.4 V is joined across a resistor. What is its resistance (in ohms)?
  33. 33.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) becomes zero (c) stays the same (d) gets smaller
  34. 34.💡 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) does not light (c) may burn out
  35. 35.🔺 A current of 50 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
  36. 36.🧾 A 500 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
  37. 37.🧮 Five equal 500 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
  38. 38.🔺 A current of 2.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
  39. 39.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
  40. 40.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?

Answer key

  1. 4500
  2. P = V × I
  3. 4
  4. 63
  5. 1.5
  6. 10
  7. 1 kilowatt-hour (kWh)
  8. 1
  9. 9400
  10. how much a part resists
  11. a buzzer
  12. 5
  13. 5
  14. 5 %
  15. an LED lamp
  16. LED
  17. False
  18. 8.7
  19. may burn out
  20. senses how bright it is
  21. 8
  22. less than either one
  23. 120
  24. R = V ÷ I
  25. 3
  26. 4000
  27. 0.5
  28. a narrow pipe
  29. 2.68
  30. wastes electricity
  31. buzzer
  32. 220
  33. gets smaller
  34. may burn out
  35. 100
  36. 3
  37. 100
  38. 15
  39. 0.15
  40. 102

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