Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 2 · 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.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
2. 2.Which of these wastes electricity? (a) use daylight to read (b) use old filament bulbs (c) unplug idle chargers (d) use LED lamps
3. 3.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
4. 4.🔺 A current of 3 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🔺 A current of 2 A flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V ÷ I (c) R = V × I (d) R = V + I
7. 7.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 270 Ω resistor? (a) red-violet-black (b) red-violet-brown (c) violet-red-brown (d) red-violet-red
8. 8.📏 How many kilo-ohms (kΩ) is 3000 Ω? =
9. 9.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 25 % (d) 50 %
10. 10.🌈 Which band is read first on a resistor? (a) the gold band (b) any band (c) the one nearest an end (d) the widest gap
11. 11.🧮 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)?
12. 12.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
13. 13.🔺 A 2 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
14. 14.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
15. 15.🌈 In the resistor colour code, which number does black stand for?
16. 16.🔺 A current of 0.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
17. 17.True or false: to iron one shirt at a time wastes electricity. (a) True (b) False
18. 18.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
19. 19.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
20. 20.💡 Does it save or waste electricity to leave fridge door open? (a) wastes electricity (b) saves electricity
21. 21.🔺 A current of 20 mA flows when 9.4 V is joined across a resistor. What is its resistance (in ohms)?
22. 22.What does a motor do? (a) makes things spin (b) lets current go one way (c) has coloured bands (d) limits the current
23. 23.Which of these wastes electricity? (a) leave the TV on standby (b) close the fridge quickly (c) switch off empty rooms (d) use LED lamps
24. 24.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
25. 25.🔺 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
26. 26.🧮 Resistors of 220 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
27. 27.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) use daylight to read (c) use LED lamps (d) run fans in empty rooms
28. 28.🧮 A 4 V battery is joined to 6 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
29. 29.🔍 Which is the odd one out? (a) leave fridge door open (b) leave the TV on standby (c) switch off empty rooms (d) iron one shirt at a time
30. 30.Which of these is measured in ohms (Ω)? (a) how much a part resists (b) voltage (c) the flow of charge (d) current
31. 31.What does a thermistor do? (a) senses how hot it is (b) stores a little charge (c) turns a fan or wheels (d) has coloured bands
32. 32.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 1000 Ω resistor? (a) brown-black-brown (b) brown-black-orange (c) red-brown-red (d) brown-black-red
33. 33.🌈 A resistor has the colour bands red, white, red. What is its value (in ohms)?
34. 34.💡 Why does an LED need a resistor in series? (a) to store charge (b) to change its colour (c) to limit the current (d) to make it brighter
35. 35.🧮 A 2.2 V battery is joined to 3 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
36. 36.🔺 A current of 20 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.⚡ A 3 W device works on 1.5 V. What current does it take (in amperes)? =
38. 38.🧩 Which component has coloured bands? (a) resistor (b) thermistor (c) diode (d) capacitor
39. 39.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = V × I (d) P = I ÷ V
40. 40.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

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