Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 644 · 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.💡 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
2. 2.What does a capacitor do? (a) boosts a small signal (b) blows if current is high (c) smooths a wobbly supply (d) lets current go one way
3. 3.🔺 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
4. 4.True or false: on an LED, the leg by the flat edge is the anode (+). (a) False (b) True
5. 5.🌈 A resistor has the colour bands red, green, brown. What is its value (in ohms)?
6. 6.🔺 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
7. 7.Which of these wastes electricity? (a) use LED lamps (b) close the fridge quickly (c) unplug idle chargers (d) run fans in empty rooms
8. 8.True or false: to use old filament bulbs wastes electricity. (a) False (b) True
9. 9.🧮 A 10 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)?
10. 10.🧩 Which component makes a beeping sound? (a) LED (b) diode (c) buzzer (d) LDR
11. 11.💡 An LED is joined to a 3 V battery through a 330 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
12. 12.True or false: the flow of charge is measured in amperes (A). (a) True (b) False
13. 13.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
14. 14.🔺 A 15 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
15. 15.🔺 A current of 10 mA flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
16. 16.Which of these saves electricity? (a) leave the TV on standby (b) close the fridge quickly (c) run fans in empty rooms (d) leave fridge door open
17. 17.🧩 A capacitor in a circuit can … (a) store charge briefly (b) make light (c) spin a wheel (d) measure heat
18. 18.📏 How many amperes (A) is 2160 mA? =
19. 19.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
20. 20.🌈 In the resistor colour code, which number does brown stand for?
21. 21.📏 How many amperes (A) is 1940 mA? =
22. 22.What does a potentiometer do? (a) is a resistance knob (b) glows using little power (c) has coloured bands (d) blows if current is high
23. 23.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🔺 A current of 0.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 4 hours. How many watt-hours (Wh) are saved?
26. 26.🔺 A 5 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
27. 27.🧾 A 50 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
28. 28.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
29. 29.What does a buzzer do? (a) is a resistance knob (b) stores a little charge (c) beeps for an alarm (d) makes things spin
30. 30.True or false: to use LED lamps wastes electricity. (a) False (b) True
31. 31.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 21000 Ω resistor? (a) red-brown-yellow (b) red-brown-red (c) red-brown-orange (d) brown-red-orange
32. 32.⚡ A device works on 24 V and takes 2 A. What is its power (in watts)? =
33. 33.📏 How many milliamperes (mA) is 1.56 A?
34. 34.True or false: a resistor stores a little charge. (a) True (b) False
35. 35.🌈 A resistor has the colour bands blue, brown, red. What is its value (in ohms)?
36. 36.True or false: the voltmeter measures current. (a) True (b) False
37. 37.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
38. 38.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🔺 A current of 3 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.True or false: a thermistor makes things spin. (a) True (b) False

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