Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 426 · 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.🔺 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
2. 2.Which of these wastes electricity? (a) use daylight to read (b) run fans in empty rooms (c) set the AC to 24 °C (d) unplug idle chargers
3. 3.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
4. 4.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
5. 5.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
6. 6.What does a resistor do? (a) has coloured bands (b) beeps for an alarm (c) senses how hot it is (d) turns a fan or wheels
7. 7.📏 How many milliamperes (mA) is 2.98 A?
8. 8.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
9. 9.📏 In the water-pipe picture of a circuit, current is like … (a) a narrow pipe (b) the flow of water (c) the water pressure (d) the pipe colour
10. 10.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) less than either one (d) their sum
11. 11.⚡ A 3 W device works on 3 V. What current does it take (in amperes)? =
12. 12.What does an LDR do? (a) boosts a small signal (b) has coloured bands (c) limits the current (d) senses how bright it is
13. 13.🌈 In the resistor colour code, which number does grey stand for?
14. 14.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 56 Ω resistor? (a) green-blue-brown (b) green-blue-black (c) blue-blue-black (d) blue-green-black
15. 15.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
16. 16.What does an LED do? (a) boosts a small signal (b) glows using little power (c) beeps for an alarm (d) stores a little charge
17. 17.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4600 Ω resistor? (a) blue-yellow-red (b) yellow-blue-brown (c) yellow-blue-orange (d) yellow-blue-red
18. 18.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a filament bulb (c) an oil lamp (d) a candle
19. 19.🧩 Which component limits the current? (a) fuse (b) transistor (c) LDR (d) resistor
20. 20.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a capacitor (c) a diode (d) a buzzer
21. 21.True or false: a resistor limits the current. (a) True (b) False
22. 22.🔺 A current of 1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
23. 23.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
24. 24.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to store charge (d) to limit the current
25. 25.⚡ A 3 W device works on 6 V. What current does it take (in amperes)? =
26. 26.🧮 An 8.5 V battery is joined to 5 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
27. 27.📏 How many kilo-ohms (kΩ) is 300 Ω? =
28. 28.🧩 Which part changes electrical energy into movement? (a) an LED (b) a fuse (c) a resistor (d) a motor
29. 29.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 6.5 V supply. What current flows (in mA)?
30. 30.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
31. 31.🧾 A 250 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
32. 32.True or false: a thermistor beeps for an alarm. (a) False (b) True
33. 33.🔺 A 4 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
34. 34.🧮 A 470 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
35. 35.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.True or false: to set the AC to 24 °C saves electricity. (a) False (b) True
37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 15 Ω resistor? (a) brown-green-brown (b) red-green-black (c) green-brown-black (d) brown-green-black
38. 38.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) zero (d) smaller
39. 39.🔺 A current of 0.25 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
40. 40.📏 How many kilo-ohms (kΩ) is 8600 Ω? =

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