Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 821 · 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.True or false: the voltmeter measures voltage. (a) True (b) False
2. 2.🌈 A resistor has the colour bands yellow, grey, red. What is its value (in ohms)?
3. 3.⚡ A 2.4 W device works on 12 V. What current does it take (in amperes)? =
4. 4.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
5. 5.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
6. 6.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) measure heat (d) spin a wheel
7. 7.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
8. 8.📏 Which unit measures power? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
9. 9.💡 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)?
10. 10.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?
11. 11.📏 How many amperes (A) is 1840 mA? =
12. 12.🔺 A 50 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
13. 13.🧾 A family uses 140 units of electricity in a month and each unit costs ₹5. What is the bill (in ₹)?
14. 14.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
15. 15.💡 What does LED stand for? (a) low energy device (b) light-emitting diode (c) large electric dial (d) light energy dial
16. 16.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets smaller (c) becomes zero (d) gets bigger
17. 17.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = I ÷ V (c) R = V + I (d) R = V × I
19. 19.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
20. 20.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
21. 21.⚡ A 72 W device works on 24 V. What current does it take (in amperes)? =
22. 22.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
23. 23.🔺 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
24. 24.🌈 A resistor has the colour bands red, black, brown. What is its value (in ohms)?
25. 25.📏 Which unit measures how much a part resists? (a) watt (W) (b) ampere (A) (c) ohm (Ω) (d) volt (V)
26. 26.💡 Does it save or waste electricity to use old filament bulbs? (a) wastes electricity (b) saves electricity
27. 27.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 ampere (d) 1 watt
28. 28.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
29. 29.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the length of a wire (d) the size of a cell
30. 30.📏 How many kilowatts (kW) is 2850 W? =
31. 31.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
32. 32.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
33. 33.🔺 A current of 2.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
34. 34.True or false: the voltmeter measures current. (a) False (b) True
35. 35.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) the flow of water (c) a bigger tank (d) a narrow pipe
36. 36.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🔺 A 2.4 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
38. 38.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an LED lamp (c) an oil lamp (d) a filament bulb
40. 40.🔺 A current of 20 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?

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