Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 244 · 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 current of 0.25 A flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
2. 2.🧮 A 1.4 V battery is joined to 8 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
3. 3.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
4. 4.True or false: a capacitor lets current go one way. (a) True (b) False
5. 5.📏 How many watts (W) is 0.3 kW?
6. 6.💡 What does LED stand for? (a) low energy device (b) light-emitting diode (c) light energy dial (d) large electric dial
7. 7.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V × I (d) P = V ÷ I
8. 8.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
9. 9.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
10. 10.🔺 A current of 25 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
11. 11.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) measure heat (d) store charge briefly
12. 12.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
13. 13.🌈 In the resistor colour code, which number does red stand for?
14. 14.⚡ A 1.8 W device works on 9 V. What current does it take (in amperes)? =
15. 15.🧩 Which part changes electrical energy into movement? (a) a fuse (b) an LED (c) a resistor (d) a motor
16. 16.📏 How many kilo-ohms (kΩ) is 700 Ω? =
17. 17.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) stay the same (c) zero (d) smaller
18. 18.True or false: current is measured in ohms (Ω). (a) False (b) True
19. 19.What does a resistor do? (a) turns a fan or wheels (b) limits the current (c) smooths a wobbly supply (d) senses how bright it is
20. 20.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 5 % (c) 50 % (d) 0 %
21. 21.🧮 A 50 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
22. 22.🔺 A current of 0.2 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
23. 23.⚡ A 7.5 W device works on 5 V. What current does it take (in amperes)? =
24. 24.Which of these wastes electricity? (a) run fans in empty rooms (b) use LED lamps (c) unplug idle chargers (d) close the fridge quickly
25. 25.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the size of a cell (d) the length of a wire
26. 26.True or false: the flow of charge is measured in amperes (A). (a) False (b) True
27. 27.🔺 A 3 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
28. 28.🧮 A 1.5 V battery is joined to 2 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
29. 29.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
30. 30.🔍 Which is the odd one out? (a) close the fridge quickly (b) switch off empty rooms (c) use old filament bulbs (d) set the AC to 24 °C
31. 31.🔺 A current of 0.2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🔺 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
33. 33.🔺 A current of 1 A flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.🔺 A current of 10 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
35. 35.True or false: the voltmeter is joined in series. (a) False (b) True
36. 36.🌈 A resistor has the colour bands brown, violet, red. What is its value (in ohms)?
37. 37.🔺 A current of 40 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🔺 A current of 0.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
39. 39.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
40. 40.🌈 In the resistor colour code, which number does blue stand for?

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