Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 264 · 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.⚡ Power tells us … (a) the length of a wire (b) the colour of light (c) the size of a cell (d) energy used each second
2. 2.True or false: a potentiometer turns a fan or wheels. (a) True (b) False
3. 3.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
4. 4.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
5. 5.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
6. 6.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
7. 7.🔺 A current of 40 mA flows when 16 V is joined across a resistor. What is its resistance (in ohms)?
8. 8.🔺 A current of 0.1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
9. 9.⚡ A device works on 6 V and takes 3 A. What is its power (in watts)? =
10. 10.Which of these wastes electricity? (a) use LED lamps (b) switch off empty rooms (c) set the AC to 24 °C (d) run fans in empty rooms
11. 11.True or false: the ammeter measures current. (a) False (b) True
12. 12.🧮 Resistors of 100 Ω, 50 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
13. 13.🧩 A capacitor in a circuit can … (a) store charge briefly (b) measure heat (c) make light (d) spin a wheel
14. 14.🧾 A 500 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
15. 15.🌈 A resistor has the colour bands red, red, black. What is its value (in ohms)?
16. 16.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) lights up (b) may burn out (c) does not light
17. 17.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
18. 18.🔺 A current of 40 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🔺 A 22.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
20. 20.True or false: to switch off empty rooms wastes electricity. (a) False (b) True
21. 21.📏 Which unit measures power? (a) ohm (Ω) (b) watt (W) (c) ampere (A) (d) volt (V)
22. 22.Which of these saves electricity? (a) leave the TV on standby (b) run fans in empty rooms (c) use old filament bulbs (d) set the AC to 24 °C
23. 23.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a motor (c) a resistor (d) an LED
24. 24.🔍 Which is the odd one out? (a) close the fridge quickly (b) use daylight to read (c) unplug idle chargers (d) leave the TV on standby
25. 25.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
26. 26.📏 In the water-pipe picture of a circuit, current is like … (a) the pipe colour (b) the flow of water (c) a narrow pipe (d) the water pressure
27. 27.What does a thermistor do? (a) senses how hot it is (b) is a resistance knob (c) beeps for an alarm (d) limits the current
28. 28.🔺 A current of 10 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
29. 29.🌈 A resistor has the colour bands red, white, orange. What is its value in kilo-ohms (kΩ)? =
30. 30.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 97 Ω resistor? (a) brown-violet-black (b) white-violet-black (c) white-violet-brown (d) violet-white-black
31. 31.What does an LED do? (a) makes a beeping sound (b) smooths a wobbly supply (c) glows using little power (d) lets current go one way
32. 32.What does an LDR do? (a) blows if current is high (b) turns a fan or wheels (c) senses how hot it is (d) senses how bright it is
33. 33.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🌈 Which band is read first on a resistor? (a) the gold band (b) any band (c) the one nearest an end (d) the widest gap
35. 35.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V ÷ R (c) I = V × R (d) I = V + R
36. 36.🔺 A 3 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
37. 37.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
38. 38.🧮 Resistors of 33 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
39. 39.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V ÷ I (c) R = V + I (d) R = V × I

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