Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 412 · 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 beeps for an alarm? (a) transistor (b) buzzer (c) LED (d) thermistor
2. 2.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = I ÷ V (d) R = V + I
3. 3.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity
4. 4.🧮 Three equal 60 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
5. 5.🔺 A 25 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
6. 6.🧮 Resistors of 68 Ω, 22 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
7. 7.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to change its colour (d) to limit the current
8. 8.🧩 Which component blows if current is high? (a) thermistor (b) resistor (c) fuse (d) motor
9. 9.📏 How many milliamperes (mA) is 2.46 A?
10. 10.🔺 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
11. 11.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V × I (d) P = V + I
12. 12.🌈 In the resistor colour code, which number does brown stand for?
13. 13.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 25 % (c) 50 % (d) 0 %
14. 14.💡 What does LED stand for? (a) light energy dial (b) large electric dial (c) low energy device (d) light-emitting diode
15. 15.True or false: to switch off empty rooms wastes electricity. (a) True (b) False
16. 16.🔺 A current of 0.5 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
17. 17.🧮 Resistors of 68 Ω, 220 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
18. 18.🔺 An 18.8 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
19. 19.🧮 A 10 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)?
20. 20.🧮 Four equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
21. 21.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
22. 22.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = I + R (c) V = R ÷ I (d) V = I ÷ R
23. 23.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) any band (d) the gold band
24. 24.🧩 Which part changes electrical energy into movement? (a) an LED (b) a resistor (c) a fuse (d) a motor
25. 25.🔺 A current of 0.1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
26. 26.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
27. 27.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 61000 Ω resistor? (a) blue-brown-red (b) blue-brown-yellow (c) brown-blue-orange (d) blue-brown-orange
28. 28.🧮 A 33 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
29. 29.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
30. 30.True or false: a thermistor senses how hot it is. (a) True (b) False
31. 31.💡 A red LED uses 2 V and should get 10 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
32. 32.🔺 A current of 1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🌈 A resistor has the colour bands blue, white, black. What is its value (in ohms)?
34. 34.⚡ A 6 W device works on 12 V. What current does it take (in amperes)? =
35. 35.True or false: on an LED, the leg by the flat edge is the anode (+). (a) False (b) True
36. 36.🧩 Which component limits the current? (a) thermistor (b) diode (c) resistor (d) capacitor
37. 37.🔍 Which is the odd one out? (a) use old filament bulbs (b) leave the TV on standby (c) set the AC to 24 °C (d) iron one shirt at a time
38. 38.📏 How many milliamperes (mA) is 0.72 A?
39. 39.🧩 Which component turns a fan or wheels? (a) fuse (b) potentiometer (c) capacitor (d) motor
40. 40.🧮 A 47 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)?

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