Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 29 · 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 part changes electrical energy into sound? (a) a capacitor (b) a diode (c) a buzzer (d) a resistor
2. 2.🔺 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
3. 3.📏 Which unit measures resistance? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
4. 4.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
5. 5.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
6. 6.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
7. 7.🧾 A 100 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
8. 8.True or false: the ammeter is joined in series. (a) False (b) True
9. 9.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
10. 10.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = I ÷ V (d) P = V ÷ I
11. 11.Which of these is measured in amperes (A)? (a) the push of a cell (b) voltage (c) resistance (d) the flow of charge
12. 12.⚡ A device works on 6 V and takes 0.1 A. What is its power (in watts)? =
13. 13.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
14. 14.🔺 A current of 0.25 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
15. 15.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 2300 Ω resistor? (a) red-orange-orange (b) orange-red-red (c) red-orange-brown (d) red-orange-red
16. 16.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to store charge (c) to make it brighter (d) to change its colour
17. 17.🔺 A 6.6 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
18. 18.⚡ A 6 W device works on 24 V. What current does it take (in amperes)? =
19. 19.What does a motor do? (a) senses how bright it is (b) stores a little charge (c) makes things spin (d) senses how hot it is
20. 20.🌈 A resistor has the colour bands grey, white, black. What is its value (in ohms)?
21. 21.True or false: the push of a cell is measured in watts (W). (a) True (b) False
22. 22.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
23. 23.True or false: an LED limits the current. (a) False (b) True
24. 24.🧮 A 4.5 V battery is joined to 3 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
25. 25.⚡ A 0.3 W device works on 1.5 V. What current does it take (in amperes)? =
26. 26.🔺 A 6 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
27. 27.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
28. 28.📏 Voltmeter or ammeter: which one is joined in series? (a) ammeter (b) voltmeter
29. 29.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) stay the same (d) zero
30. 30.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
31. 31.🔺 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
32. 32.🔺 A current of 50 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🔺 A current of 20 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V + I (c) R = V ÷ I (d) R = I ÷ V
35. 35.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
36. 36.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the colour of light (d) the size of a cell
37. 37.True or false: a potentiometer boosts a small signal. (a) False (b) True
38. 38.True or false: to unplug idle chargers wastes electricity. (a) True (b) False
39. 39.🔺 A 15 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
40. 40.🔺 A 10 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =

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