Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 138 · 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 buzzer (b) a diode (c) a resistor (d) a capacitor
2. 2.True or false: energy used each second is measured in ohms (Ω). (a) True (b) False
3. 3.🔺 A current of 0.1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🧩 Which component smooths a wobbly supply? (a) thermistor (b) capacitor (c) LED (d) motor
5. 5.🌈 A resistor has the colour bands orange, grey, yellow. What is its value in kilo-ohms (kΩ)? =
6. 6.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
7. 7.🧮 A 33 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
8. 8.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
9. 9.True or false: a diode lets current go one way. (a) True (b) False
10. 10.🔺 A 1.2 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
11. 11.🔺 A current of 0.5 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
12. 12.True or false: the flow of charge is measured in amperes (A). (a) True (b) False
13. 13.💡 An LED is joined to a 6 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) does not light (b) lights up (c) may burn out
14. 14.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets bigger (d) gets smaller
15. 15.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) a bigger tank (c) the flow of water (d) a narrow pipe
16. 16.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) stay the same (d) smaller
17. 17.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = R ÷ V (c) I = V × R (d) I = V ÷ R
18. 18.True or false: the flow of charge is measured in watts (W). (a) True (b) False
19. 19.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 ampere (c) 1 volt (d) 1 kilowatt-hour (kWh)
20. 20.🔺 A current of 1.5 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
22. 22.True or false: the voltmeter measures voltage. (a) True (b) False
23. 23.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) measure heat (d) store charge briefly
25. 25.True or false: on an LED, the leg by the flat edge is the anode (+). (a) False (b) True
26. 26.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
27. 27.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
28. 28.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?
29. 29.⚡ A 2.4 W device works on 24 V. What current does it take (in amperes)? =
30. 30.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
31. 31.🧩 Which component is a resistance knob? (a) buzzer (b) LDR (c) capacitor (d) potentiometer
32. 32.🧮 Resistors of 10 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
33. 33.Which of these is measured in watts (W)? (a) the flow of charge (b) current (c) power (d) the push of a cell
34. 34.🔺 A current of 25 mA flows when 5.5 V is joined across a resistor. What is its resistance (in ohms)?
35. 35.True or false: to use LED lamps wastes electricity. (a) True (b) False
36. 36.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.🔺 A 12.5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
38. 38.🔺 A current of 0.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
39. 39.True or false: energy used each second is measured in watts (W). (a) False (b) True
40. 40.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?

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