Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 769 · 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.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) zero (d) stay the same
2. 2.🌈 A resistor has the colour bands brown, green, black. What is its value (in ohms)?
3. 3.🌈 A resistor has the colour bands brown, grey, brown. What is its value (in ohms)?
4. 4.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
5. 5.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
6. 6.🌈 In the resistor colour code, which number does white stand for?
7. 7.True or false: a capacitor smooths a wobbly supply. (a) False (b) True
8. 8.Which of these wastes electricity? (a) leave the TV on standby (b) set the AC to 24 °C (c) switch off empty rooms (d) close the fridge quickly
9. 9.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 100 (b) 10 (c) 1024 (d) 1000
10. 10.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
11. 11.🌈 In the resistor colour code, which number does red stand for?
12. 12.🔺 A 15 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
13. 13.🔺 A current of 2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
14. 14.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
15. 15.⚡ A 0.3 W device works on 1.5 V. What current does it take (in amperes)? =
16. 16.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
17. 17.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
18. 18.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I ÷ R (c) V = I × R (d) V = R ÷ I
19. 19.📏 Which unit measures how much a part resists? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
20. 20.🔺 A current of 25 mA flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.🧩 A capacitor in a circuit can … (a) spin a wheel (b) store charge briefly (c) make light (d) measure heat
22. 22.⚡ A device works on 24 V and takes 0.25 A. What is its power (in watts)? =
23. 23.🔺 A current of 25 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
24. 24.What does a buzzer do? (a) stores a little charge (b) blows if current is high (c) senses how bright it is (d) makes a beeping sound
25. 25.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 0 % (d) 5 %
26. 26.🔺 A current of 25 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
27. 27.💡 Does it save or waste electricity to close the fridge quickly? (a) wastes electricity (b) saves electricity
28. 28.🔺 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
29. 29.Which of these wastes electricity? (a) unplug idle chargers (b) set the AC to 24 °C (c) use daylight to read (d) leave fridge door open
30. 30.⚡ An 18 W device works on 6 V. What current does it take (in amperes)? =
31. 31.What does a diode do? (a) limits the current (b) glows using little power (c) has coloured bands (d) lets current go one way
32. 32.Which of these saves electricity? (a) iron one shirt at a time (b) run fans in empty rooms (c) leave fridge door open (d) close the fridge quickly
33. 33.🧾 A 500 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
34. 34.🌈 A resistor has the colour bands blue, orange, yellow. What is its value in kilo-ohms (kΩ)? =
35. 35.🧮 A 2 V battery is joined to 12 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
36. 36.🔺 A current of 3 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🔺 A current of 3 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
38. 38.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
39. 39.🧩 Which component makes a beeping sound? (a) buzzer (b) capacitor (c) diode (d) LED
40. 40.🔺 A 4 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =

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