Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 612 · 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.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
2. 2.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
3. 3.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a filament bulb (c) a candle (d) an oil lamp
4. 4.💡 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)?
5. 5.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) energy used each second (d) the colour of light
6. 6.What does an LDR do? (a) stores a little charge (b) smooths a wobbly supply (c) senses how hot it is (d) senses how bright it is
7. 7.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V + I (c) R = V × I (d) R = I ÷ V
8. 8.What does a resistor do? (a) beeps for an alarm (b) blows if current is high (c) limits the current (d) turns a fan or wheels
9. 9.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
10. 10.True or false: an LDR is a resistance knob. (a) True (b) False
11. 11.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
12. 12.🔺 A 12 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
13. 13.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
14. 14.🔺 A current of 40 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
15. 15.Which of these is measured in watts (W)? (a) current (b) the flow of charge (c) resistance (d) energy used each second
16. 16.Which of these saves electricity? (a) use daylight to read (b) iron one shirt at a time (c) leave fridge door open (d) leave the TV on standby
17. 17.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) a fuse (d) an LED
18. 18.🌈 A resistor has the colour bands red, white, orange. What is its value in kilo-ohms (kΩ)? =
19. 19.📏 How many amperes (A) is 210 mA? =
20. 20.🧮 A 1.4 V battery is joined to 3 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
21. 21.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = V ÷ I (d) P = I ÷ V
22. 22.⚡ A 2.4 W device works on 12 V. What current does it take (in amperes)? =
23. 23.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 10 (d) 1000
24. 24.💡 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)?
25. 25.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
26. 26.🔺 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
27. 27.What does an LED do? (a) blows if current is high (b) stores a little charge (c) glows using little power (d) turns a fan or wheels
28. 28.🔺 A current of 0.1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
29. 29.📏 How many kilowatts (kW) is 2150 W? =
30. 30.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) smaller (d) bigger
31. 31.🔺 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
32. 32.🌈 A resistor has the colour bands white, brown, black. What is its value (in ohms)?
33. 33.🔍 Which is the odd one out? (a) unplug idle chargers (b) leave the TV on standby (c) iron one shirt at a time (d) run fans in empty rooms
34. 34.True or false: to run fans in empty rooms saves electricity. (a) False (b) True
35. 35.⚡ A 12 W device works on 6 V. What current does it take (in amperes)? =
36. 36.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
37. 37.🧮 A 470 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
38. 38.🔺 A current of 20 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
40. 40.⚡ A device works on 24 V and takes 0.2 A. What is its power (in watts)? =

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