Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 596 · 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 resistor has the colour bands blue, brown, brown. What is its value (in ohms)?
2. 2.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
3. 3.⚡ A 2.5 W device works on 5 V. What current does it take (in amperes)? =
4. 4.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 3300 Ω resistor? (a) orange-orange-orange (b) orange-orange-brown (c) orange-orange-red (d) orange-yellow-red
5. 5.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an LED lamp (d) an oil lamp
6. 6.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 4 V supply. What current flows (in mA)?
7. 7.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
8. 8.🌈 In the resistor colour code, which number does black stand for?
9. 9.True or false: to use daylight to read wastes electricity. (a) False (b) True
10. 10.🧾 A 250 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
11. 11.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V ÷ I (c) R = I ÷ V (d) R = V × I
12. 12.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 74 Ω resistor? (a) violet-yellow-brown (b) yellow-violet-black (c) grey-yellow-black (d) violet-yellow-black
14. 14.🔺 A 5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
15. 15.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
16. 16.🌈 A resistor has the colour bands brown, brown, yellow. What is its value in kilo-ohms (kΩ)? =
17. 17.💡 Does it save or waste electricity to unplug idle chargers? (a) saves electricity (b) wastes electricity
18. 18.🧮 A 7.5 V battery is joined to 3 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
19. 19.True or false: a transistor boosts a small signal. (a) False (b) True
20. 20.🔺 A current of 0.1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
22. 22.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to change its colour (c) to store charge (d) to make it brighter
23. 23.⚡ Which formula gives electric power? (a) P = V × I (b) P = V + I (c) P = I ÷ V (d) P = V ÷ I
24. 24.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
25. 25.🧾 A 500 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
26. 26.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
27. 27.True or false: power is measured in amperes (A). (a) False (b) True
28. 28.True or false: an LDR senses how bright it is. (a) False (b) True
29. 29.🧩 Which component turns a fan or wheels? (a) potentiometer (b) LED (c) motor (d) diode
30. 30.What does a transistor do? (a) stores a little charge (b) boosts a small signal (c) lets current go one way (d) limits the current
31. 31.🧮 A 470 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
32. 32.💡 Does it save or waste electricity to use LED lamps? (a) saves electricity (b) wastes electricity
33. 33.🧾 A family uses 70 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
34. 34.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) bigger (d) zero
35. 35.🔺 A current of 1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🔺 A current of 2.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🔺 A current of 1.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🧮 A 10 V battery is joined to 2 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
39. 39.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
40. 40.🔺 A 2.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =

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