Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 925 · 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.What does a fuse do? (a) makes things spin (b) turns a fan or wheels (c) blows if current is high (d) makes a beeping sound
2. 2.💡 A red LED uses 2 V and should get 10 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
3. 3.What does an LDR do? (a) has coloured bands (b) senses how hot it is (c) senses how bright it is (d) glows using little power
4. 4.🔺 A current of 2.5 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
6. 6.🌈 A resistor has the colour bands grey, brown, orange. What is its value in kilo-ohms (kΩ)? =
7. 7.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = R ÷ V (c) I = V × R (d) I = V ÷ R
8. 8.🔺 A current of 2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
9. 9.⚡ A 4.8 W device works on 24 V. What current does it take (in amperes)? =
10. 10.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
11. 11.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 80000 Ω resistor? (a) white-grey-orange (b) grey-black-yellow (c) grey-black-orange (d) grey-black-red
12. 12.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
13. 13.True or false: the voltmeter measures current. (a) True (b) False
14. 14.⚡ A device works on 3 V and takes 3 A. What is its power (in watts)? =
15. 15.🔺 A current of 2 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
16. 16.🧩 Which component lets current go one way? (a) transistor (b) LDR (c) fuse (d) diode
17. 17.🧮 A 33 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
18. 18.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🔺 A current of 0.25 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
20. 20.True or false: a buzzer has coloured bands. (a) False (b) True
21. 21.What does a diode do? (a) smooths a wobbly supply (b) glows using little power (c) lets current go one way (d) boosts a small signal
22. 22.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 0 % (d) 25 %
23. 23.⚡ A 27 W device works on 9 V. What current does it take (in amperes)? =
24. 24.🧩 Which component has coloured bands? (a) motor (b) resistor (c) fuse (d) thermistor
25. 25.🔍 Which is the odd one out? (a) leave fridge door open (b) use LED lamps (c) switch off empty rooms (d) use daylight to read
26. 26.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
27. 27.💡 Does it save or waste electricity to iron one shirt at a time? (a) saves electricity (b) wastes electricity
28. 28.🌈 A resistor has the colour bands yellow, white, orange. What is its value (in ohms)?
29. 29.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 10 (d) 1000
30. 30.True or false: the voltmeter is joined across a part. (a) True (b) False
31. 31.⚡ A 12 W device works on 6 V. What current does it take (in amperes)? =
32. 32.🧮 A 20 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
33. 33.🔺 A current of 1.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a filament bulb (d) a candle
35. 35.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
36. 36.True or false: the ammeter measures voltage. (a) False (b) True
37. 37.⚡ A 3 W device works on 12 V. What current does it take (in amperes)? =
38. 38.🔺 A current of 0.2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 88 Ω resistor? (a) grey-white-black (b) grey-grey-brown (c) white-grey-black (d) grey-grey-black
40. 40.📏 How many milliamperes (mA) is 1.31 A?

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