Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 494 · 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.True or false: an LED blows if current is high. (a) True (b) False
2. 2.🔺 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
3. 3.📏 How many watts (W) is 4.7 kW?
4. 4.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🧮 Resistors of 20 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
6. 6.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.⚡ A 15 W device works on 5 V. What current does it take (in amperes)? =
8. 8.📏 How many kilo-ohms (kΩ) is 9400 Ω? =
9. 9.🌈 In the resistor colour code, which number does violet stand for?
10. 10.⚡ A 0.9 W device works on 9 V. What current does it take (in amperes)? =
11. 11.🔺 A 15 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
12. 12.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
13. 13.💡 An LED is joined to a 5 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) does not light (c) lights up
14. 14.🧩 Which component makes things spin? (a) thermistor (b) potentiometer (c) motor (d) LED
15. 15.🧩 Which component senses how hot it is? (a) capacitor (b) thermistor (c) LDR (d) buzzer
16. 16.📏 How many ohms (Ω) is 5.3 kΩ?
17. 17.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 2600 Ω resistor? (a) red-blue-red (b) red-blue-brown (c) blue-red-red (d) red-blue-orange
18. 18.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 15000 Ω resistor? (a) brown-green-orange (b) brown-green-yellow (c) green-brown-orange (d) brown-green-red
19. 19.🌈 A resistor has the colour bands brown, blue, yellow. What is its value in kilo-ohms (kΩ)? =
20. 20.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) bigger (d) stay the same
22. 22.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
23. 23.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 0 % (d) 5 %
24. 24.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
25. 25.Which of these wastes electricity? (a) set the AC to 24 °C (b) use daylight to read (c) unplug idle chargers (d) run fans in empty rooms
26. 26.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a diode (c) a capacitor (d) a buzzer
27. 27.🔺 A current of 40 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
29. 29.Which of these is measured in ohms (Ω)? (a) energy used each second (b) power (c) how much a part resists (d) voltage
30. 30.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to change its colour (c) to store charge (d) to make it brighter
31. 31.What does a resistor do? (a) smooths a wobbly supply (b) has coloured bands (c) senses how bright it is (d) glows using little power
32. 32.🧮 A 100 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)?
33. 33.🧩 A capacitor in a circuit can … (a) store charge briefly (b) measure heat (c) spin a wheel (d) make light
34. 34.⚡ A 24 W device works on 12 V. What current does it take (in amperes)? =
35. 35.💡 An LED is joined to a 5 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) does not light (c) lights up
36. 36.⚡ A device works on 12 V and takes 1 A. What is its power (in watts)? =
37. 37.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
39. 39.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 110 Ω resistor? (a) brown-brown-black (b) brown-brown-brown (c) brown-brown-red (d) brown-red-brown
40. 40.💡 An LED is joined to a 6 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) may burn out (c) does not light

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