Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 36 · 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 component limits the current? (a) resistor (b) motor (c) fuse (d) thermistor
2. 2.💡 An LED is joined to a 9 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) does not light (c) lights up
3. 3.🔺 A current of 20 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
4. 4.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 3000 Ω resistor? (a) orange-black-red (b) orange-black-orange (c) orange-black-brown (d) yellow-orange-red
5. 5.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4900 Ω resistor? (a) yellow-white-orange (b) yellow-white-brown (c) yellow-white-red (d) white-yellow-red
6. 6.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the widest gap (d) the gold band
7. 7.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
8. 8.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
9. 9.💡 A red LED uses 2 V and should get 10 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
10. 10.🔺 A current of 1.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
11. 11.True or false: a transistor boosts a small signal. (a) False (b) True
12. 12.🔺 A current of 2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🧩 Which component makes a beeping sound? (a) transistor (b) buzzer (c) LED (d) resistor
14. 14.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
15. 15.⚡ A 15 W device works on 5 V. What current does it take (in amperes)? =
16. 16.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.Which of these wastes electricity? (a) close the fridge quickly (b) run fans in empty rooms (c) use daylight to read (d) set the AC to 24 °C
19. 19.📏 How many milliamperes (mA) is 0.62 A?
20. 20.🧩 Which part changes electrical energy into movement? (a) a motor (b) a fuse (c) a resistor (d) an LED
21. 21.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
22. 22.What does a buzzer do? (a) makes a beeping sound (b) senses how hot it is (c) smooths a wobbly supply (d) glows using little power
23. 23.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
24. 24.🌈 In the resistor colour code, which number does black stand for?
25. 25.True or false: the ammeter measures current. (a) True (b) False
26. 26.📏 How many kilowatts (kW) is 4450 W? =
27. 27.📏 How many kilo-ohms (kΩ) is 800 Ω? =
28. 28.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
29. 29.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
30. 30.📏 How many milliamperes (mA) is 1.51 A?
31. 31.What does a resistor do? (a) smooths a wobbly supply (b) is a resistance knob (c) limits the current (d) senses how bright it is
32. 32.🌈 A resistor has the colour bands blue, green, black. What is its value (in ohms)?
33. 33.🔺 A 10 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
34. 34.🧮 Resistors of 33 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
35. 35.🧾 A 1000 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
36. 36.🌈 A resistor has the colour bands red, brown, red. What is its value in kilo-ohms (kΩ)? =
37. 37.Which of these wastes electricity? (a) iron one shirt at a time (b) use LED lamps (c) set the AC to 24 °C (d) use daylight to read
38. 38.🌈 A resistor has the colour bands brown, red, brown. What is its value (in ohms)?
39. 39.Which of these is measured in amperes (A)? (a) power (b) voltage (c) the flow of charge (d) resistance
40. 40.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?

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