Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 182 · 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.📏 Which unit measures the push of a cell? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)
2. 2.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
3. 3.⚡ A device works on 24 V and takes 0.1 A. What is its power (in watts)? =
4. 4.💡 An LED is joined to a 5 V battery through a 1000 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) lights up (c) does not light
5. 5.What does a buzzer do? (a) senses how hot it is (b) lets current go one way (c) makes a beeping sound (d) turns a fan or wheels
6. 6.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
7. 7.🧩 Which component glows using little power? (a) LED (b) motor (c) capacitor (d) buzzer
8. 8.🧮 Resistors of 68 Ω, 68 Ω, 330 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
9. 9.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) may burn out (c) does not light
10. 10.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
11. 11.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
12. 12.🔺 A 1.2 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
13. 13.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
14. 14.🧮 Four equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
15. 15.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = V × I (d) P = I ÷ V
16. 16.🌈 A resistor has the colour bands yellow, violet, black. What is its value (in ohms)?
17. 17.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to store charge (d) to limit the current
18. 18.🧮 Resistors of 33 Ω, 33 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
19. 19.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 3000 Ω resistor? (a) yellow-orange-red (b) orange-black-brown (c) orange-black-orange (d) orange-black-red
20. 20.🌈 A resistor has the colour bands yellow, orange, orange. What is its value (in ohms)?
21. 21.Which of these wastes electricity? (a) switch off empty rooms (b) close the fridge quickly (c) use old filament bulbs (d) unplug idle chargers
22. 22.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
23. 23.🔺 A current of 1.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
24. 24.💡 An LED is joined to a 5 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) lights up (b) does not light (c) may burn out
25. 25.True or false: to iron one shirt at a time saves electricity. (a) True (b) False
26. 26.🔺 A current of 1.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
27. 27.True or false: the voltmeter measures voltage. (a) True (b) False
28. 28.🔺 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
29. 29.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
30. 30.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
31. 31.🔺 A current of 25 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🧩 Which component has coloured bands? (a) resistor (b) potentiometer (c) transistor (d) fuse
33. 33.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the gold band (d) the widest gap
34. 34.📏 Which unit measures current? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
35. 35.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.🔺 A 5.5 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
37. 37.🧮 A 12 V battery is joined to 4 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
38. 38.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 1400 Ω resistor? (a) brown-yellow-brown (b) yellow-brown-red (c) brown-yellow-orange (d) brown-yellow-red
39. 39.⚡ A 2.4 W device works on 24 V. What current does it take (in amperes)? =
40. 40.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?

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