Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 839 · 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 of these wastes electricity? (a) use LED lamps (b) unplug idle chargers (c) set the AC to 24 °C (d) iron one shirt at a time
2. 2.🧩 Which component lets current go one way? (a) diode (b) LDR (c) resistor (d) LED
3. 3.🔺 A current of 20 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
4. 4.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
5. 5.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) gets smaller (c) becomes zero (d) stays the same
6. 6.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V + R (c) I = V × R (d) I = R ÷ V
8. 8.🔺 A 0.4 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
9. 9.🧮 Resistors of 22 Ω, 330 Ω, 470 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
10. 10.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
11. 11.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
12. 12.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
14. 14.🌈 A resistor has the colour bands brown, grey, red. What is its value (in ohms)?
15. 15.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
16. 16.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
17. 17.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
18. 18.🔺 A current of 3 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
19. 19.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 2.75 V supply. What current flows (in mA)?
20. 20.🧩 Which component senses how hot it is? (a) LED (b) capacitor (c) motor (d) thermistor
21. 21.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) bigger (d) zero
22. 22.True or false: to run fans in empty rooms saves electricity. (a) True (b) False
23. 23.🌈 In the resistor colour code, which number does black stand for?
24. 24.🧩 A capacitor in a circuit can … (a) measure heat (b) make light (c) store charge briefly (d) spin a wheel
25. 25.⚡ Power tells us … (a) the length of a wire (b) the colour of light (c) energy used each second (d) the size of a cell
26. 26.💡 Does it save or waste electricity to close the fridge quickly? (a) saves electricity (b) wastes electricity
27. 27.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
28. 28.💡 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)?
29. 29.💡 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
30. 30.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
31. 31.🔺 A 0.2 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
32. 32.🔺 A current of 0.25 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 watt (d) 1 ampere
34. 34.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
35. 35.🧮 Five equal 250 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 6 V supply. What current flows (in mA)?
37. 37.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
38. 38.🔺 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
39. 39.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
40. 40.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =

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