Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 73 · 40 questions

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.

1. 1.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 4 hours. How many watt-hours (Wh) are saved?
2. 2.🔺 A current of 40 mA flows when 18.8 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 5 V supply. What current flows (in mA)?
4. 4.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V × I (c) R = V + I (d) R = I ÷ V
5. 5.🔺 A current of 0.2 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a capacitor (d) a buzzer
7. 7.⚡ A 36 W device works on 24 V. What current does it take (in amperes)? =
8. 8.⚡ Power tells us … (a) the length of a wire (b) the colour of light (c) energy used each second (d) the size of a cell
9. 9.🔺 A 20 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
10. 10.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
11. 11.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
12. 12.🔺 A 0.4 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
13. 13.🧮 A 330 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
14. 14.📏 How many amperes (A) is 2830 mA? =
15. 15.Which of these is measured in amperes (A)? (a) resistance (b) the flow of charge (c) how much a part resists (d) the push of a cell
16. 16.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
17. 17.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V × I (d) P = V + I
18. 18.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = R ÷ I (c) V = I × R (d) V = I + R
19. 19.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
20. 20.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
21. 21.What does a thermistor do? (a) senses how bright it is (b) senses how hot it is (c) has coloured bands (d) smooths a wobbly supply
22. 22.🔺 A current of 40 mA flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
23. 23.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to limit the current (d) to change its colour
24. 24.🔺 A current of 1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
25. 25.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
26. 26.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
27. 27.🌈 In the resistor colour code, which number does grey stand for?
28. 28.🔺 A current of 0.5 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
29. 29.Which of these wastes electricity? (a) use LED lamps (b) switch off empty rooms (c) run fans in empty rooms (d) close the fridge quickly
30. 30.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) bigger (d) smaller
31. 31.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) more than either one (d) their sum
32. 32.🔺 A current of 50 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🌈 A resistor has the colour bands red, orange, orange. What is its value (in ohms)?
34. 34.What does a buzzer do? (a) senses how bright it is (b) has coloured bands (c) is a resistance knob (d) makes a beeping sound
35. 35.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
36. 36.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🧾 A 100 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
38. 38.🔺 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
39. 39.🔺 A current of 50 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🔺 A current of 0.2 A flows when 1.2 V is joined across a resistor. What is its resistance (in ohms)?

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