Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 421 · 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.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
2. 2.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = I ÷ V (d) P = V + I
3. 3.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) bigger (d) smaller
4. 4.🔺 A 2 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
5. 5.🔺 A current of 2 A flows when 12 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.⚡ A device works on 12 V and takes 1.5 A. What is its power (in watts)? =
7. 7.True or false: the voltmeter is joined in series. (a) False (b) True
8. 8.⚡ A 9 W device works on 3 V. What current does it take (in amperes)? =
9. 9.📏 How many amperes (A) is 2540 mA? =
10. 10.🌈 A resistor has the colour bands white, white, black. What is its value (in ohms)?
11. 11.⚡ A 24 W device works on 24 V. What current does it take (in amperes)? =
12. 12.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 25 % (d) 50 %
13. 13.🔺 A current of 1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
14. 14.What does a resistor do? (a) smooths a wobbly supply (b) senses how hot it is (c) has coloured bands (d) makes a beeping sound
15. 15.🔺 A 20 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.What does a buzzer do? (a) makes a beeping sound (b) stores a little charge (c) smooths a wobbly supply (d) has coloured bands
17. 17.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an oil lamp (d) an LED lamp
18. 18.💡 An LED is joined to a 6 V battery through a 1000 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) lights up (b) does not light (c) may burn out
19. 19.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
20. 20.🧮 A 150 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
21. 21.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
22. 22.True or false: a fuse blows if current is high. (a) False (b) True
23. 23.🔺 A current of 2.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the gold band (c) the widest gap (d) any band
25. 25.What does a capacitor do? (a) senses how hot it is (b) is a resistance knob (c) makes a beeping sound (d) smooths a wobbly supply
26. 26.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) energy used each second (d) the colour of light
27. 27.📏 How many amperes (A) is 2340 mA? =
28. 28.🔺 A current of 50 mA flows when 25 V is joined across a resistor. What is its resistance (in ohms)?
29. 29.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = V ÷ R (c) I = V × R (d) I = R ÷ V
30. 30.🧮 Resistors of 50 Ω, 68 Ω, 33 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
31. 31.Which of these is measured in volts (V)? (a) the flow of charge (b) voltage (c) power (d) current
32. 32.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
33. 33.True or false: an LDR senses how bright it is. (a) False (b) True
34. 34.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 watt (c) 1 kilowatt-hour (kWh) (d) 1 volt
35. 35.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.🌈 In the resistor colour code, which number does blue stand for?
37. 37.🧩 Which component senses how bright it is? (a) potentiometer (b) resistor (c) LDR (d) LED
38. 38.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
39. 39.🔺 A current of 1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🧩 Which component makes things spin? (a) LDR (b) motor (c) capacitor (d) transistor

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