Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 738 · 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 6 W device works on 6 V. What current does it take (in amperes)? =
2. 2.True or false: how much a part resists is measured in volts (V). (a) True (b) False
3. 3.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
4. 4.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🔺 A 24 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
6. 6.Which of these wastes electricity? (a) use LED lamps (b) unplug idle chargers (c) switch off empty rooms (d) leave fridge door open
7. 7.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to limit the current (d) to change its colour
8. 8.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
9. 9.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
10. 10.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
11. 11.🔺 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
12. 12.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
13. 13.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
14. 14.🔺 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
15. 15.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
16. 16.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
17. 17.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
18. 18.🔺 A current of 0.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
19. 19.True or false: to use daylight to read wastes electricity. (a) True (b) False
20. 20.🧮 Resistors of 100 Ω, 47 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
21. 21.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) always zero (c) more than either one (d) their sum
22. 22.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
23. 23.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1000 (b) 1024 (c) 100 (d) 10
24. 24.🧮 Resistors of 47 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
25. 25.True or false: the ammeter is joined across a part. (a) False (b) True
26. 26.⚡ A 9 W device works on 9 V. What current does it take (in amperes)? =
27. 27.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
28. 28.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
29. 29.🔺 A current of 25 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
30. 30.💡 What does LED stand for? (a) large electric dial (b) low energy device (c) light-emitting diode (d) light energy dial
31. 31.⚡ A 6 W device works on 12 V. What current does it take (in amperes)? =
32. 32.What does a transistor do? (a) stores a little charge (b) is a resistance knob (c) blows if current is high (d) boosts a small signal
33. 33.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 50 % (d) 25 %
35. 35.🔺 A 10 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
36. 36.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
37. 37.📏 How many amperes (A) is 1270 mA? =
38. 38.⚡ A 2.25 W device works on 1.5 V. What current does it take (in amperes)? =
39. 39.📏 Which unit measures voltage? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
40. 40.🌈 A resistor has the colour bands green, red, red. What is its value in kilo-ohms (kΩ)? =

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