Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 909 · 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.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
2. 2.What does a motor do? (a) boosts a small signal (b) limits the current (c) makes things spin (d) is a resistance knob
3. 3.🔺 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
4. 4.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a candle (d) a filament bulb
5. 5.💡 An LED is joined to a 6 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
6. 6.True or false: on an LED, the shorter leg is the anode (+). (a) False (b) True
7. 7.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) may burn out (b) does not light (c) lights up
8. 8.💡 What does LED stand for? (a) light-emitting diode (b) light energy dial (c) low energy device (d) large electric dial
9. 9.🧮 A 7.5 V battery is joined to 3 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
10. 10.🌈 A resistor has the colour bands red, orange, red. What is its value (in ohms)?
11. 11.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
12. 12.🔺 A current of 25 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
13. 13.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
14. 14.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =
15. 15.True or false: to leave fridge door open saves electricity. (a) False (b) True
16. 16.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
17. 17.What does a diode do? (a) senses how bright it is (b) lets current go one way (c) has coloured bands (d) beeps for an alarm
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 4 V battery is joined to 12 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 11 Ω resistor? (a) red-brown-black (b) brown-red-black (c) brown-brown-black (d) brown-brown-brown
21. 21.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
22. 22.🔺 A current of 1.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🧩 Which component has coloured bands? (a) motor (b) transistor (c) fuse (d) resistor
24. 24.🔍 Which is the odd one out? (a) switch off empty rooms (b) leave fridge door open (c) use old filament bulbs (d) run fans in empty rooms
25. 25.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 85 Ω resistor? (a) grey-green-brown (b) green-grey-black (c) white-green-black (d) grey-green-black
26. 26.🧾 A family uses 200 units of electricity in a month and each unit costs ₹9. What is the bill (in ₹)?
27. 27.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
28. 28.🧾 A family uses 30 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
29. 29.True or false: to leave the TV on standby saves electricity. (a) True (b) False
30. 30.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 4 V supply. What current flows (in mA)?
31. 31.True or false: to iron one shirt at a time wastes electricity. (a) True (b) False
32. 32.🔺 A current of 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🧾 A family uses 80 units of electricity in a month and each unit costs ₹6. What is the bill (in ₹)?
34. 34.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to limit the current (d) to store charge
35. 35.⚡ A device works on 3 V and takes 0.1 A. What is its power (in watts)? =
36. 36.🔺 A 15 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
37. 37.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
38. 38.🔺 A 12.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
39. 39.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the flow of water (c) the water pressure (d) a bigger tank
40. 40.💡 A red LED uses 2 V and should get 20 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?

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