Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 135 · 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 resistor has the colour bands brown, orange, brown. What is its value (in ohms)?
2. 2.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
3. 3.🌈 A resistor has the colour bands white, black, black. What is its value (in ohms)?
4. 4.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
5. 5.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
6. 6.🧩 A capacitor in a circuit can … (a) make light (b) measure heat (c) spin a wheel (d) store charge briefly
7. 7.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to store charge (c) to change its colour (d) to make it brighter
8. 8.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
9. 9.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) energy used each second (d) the length of a wire
10. 10.True or false: current is measured in watts (W). (a) False (b) True
11. 11.What does a thermistor do? (a) limits the current (b) makes a beeping sound (c) senses how hot it is (d) boosts a small signal
12. 12.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.What does a capacitor do? (a) beeps for an alarm (b) limits the current (c) makes things spin (d) smooths a wobbly supply
14. 14.⚡ An 18 W device works on 6 V. What current does it take (in amperes)? =
15. 15.What does a resistor do? (a) smooths a wobbly supply (b) turns a fan or wheels (c) lets current go one way (d) has coloured bands
16. 16.🧩 Which component stores a little charge? (a) buzzer (b) capacitor (c) diode (d) LED
17. 17.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
18. 18.🔺 A current of 2.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
19. 19.⚡ A 72 W device works on 24 V. What current does it take (in amperes)? =
20. 20.What does an LDR do? (a) senses how bright it is (b) has coloured bands (c) makes things spin (d) is a resistance knob
21. 21.🔺 A current of 2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🌈 A resistor has the colour bands green, grey, yellow. What is its value in kilo-ohms (kΩ)? =
24. 24.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V × I (d) P = V ÷ I
25. 25.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
26. 26.🔺 A 5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
27. 27.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
28. 28.🌈 A resistor has the colour bands white, violet, brown. What is its value (in ohms)?
29. 29.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 900 Ω resistor? (a) white-black-red (b) brown-white-brown (c) white-black-black (d) white-black-brown
30. 30.📏 How many milliamperes (mA) is 0.07 A?
31. 31.🔺 A current of 40 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
32. 32.True or false: the push of a cell is measured in volts (V). (a) True (b) False
33. 33.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
34. 34.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
35. 35.🔺 A current of 3 A flows when 60 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
37. 37.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.🌈 A resistor has the colour bands blue, blue, black. What is its value (in ohms)?
39. 39.True or false: a transistor boosts a small signal. (a) False (b) True
40. 40.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)

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