Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 807 · 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 component has coloured bands? (a) motor (b) resistor (c) LDR (d) potentiometer
2. 2.🧮 A 220 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
3. 3.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 0 % (d) 5 %
4. 4.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = R ÷ I (c) V = I ÷ R (d) V = I × R
5. 5.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
6. 6.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.🔺 A current of 1.5 A flows when 18 V is joined across a resistor. What is its resistance (in ohms)?
8. 8.💡 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)?
9. 9.🧩 Which part changes electrical energy into movement? (a) an LED (b) a fuse (c) a resistor (d) a motor
10. 10.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
11. 11.📏 How many ohms (Ω) is 1.5 kΩ?
12. 12.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) energy used each second (d) the colour of light
13. 13.🔺 A current of 20 mA flows when 9.4 V is joined across a resistor. What is its resistance (in ohms)?
14. 14.True or false: to set the AC to 24 °C wastes electricity. (a) True (b) False
15. 15.🔺 A current of 0.25 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
16. 16.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🌈 A resistor has the colour bands grey, yellow, red. What is its value in kilo-ohms (kΩ)? =
18. 18.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a capacitor (c) a buzzer (d) a diode
19. 19.Which of these saves electricity? (a) use old filament bulbs (b) switch off empty rooms (c) leave fridge door open (d) leave the TV on standby
20. 20.True or false: an LDR senses how bright it is. (a) True (b) False
21. 21.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the gold band (c) any band (d) the widest gap
22. 22.⚡ A device works on 9 V and takes 0.25 A. What is its power (in watts)? =
23. 23.🔺 A current of 0.25 A flows when 0.5 V is joined across a resistor. What is its resistance (in ohms)?
24. 24.True or false: the flow of charge is measured in volts (V). (a) False (b) True
25. 25.🌈 In the resistor colour code, which number does green stand for?
26. 26.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an LED lamp (c) an oil lamp (d) a filament bulb
27. 27.🔺 A current of 50 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
29. 29.🔺 An 11.75 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
30. 30.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water tank lid (b) the pipe colour (c) the tap handle (d) the water pressure
31. 31.🔺 A current of 50 mA flows when 16.5 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.💡 What does LED stand for? (a) low energy device (b) large electric dial (c) light energy dial (d) light-emitting diode
33. 33.What does a thermistor do? (a) has coloured bands (b) senses how hot it is (c) lets current go one way (d) smooths a wobbly supply
34. 34.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
35. 35.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
36. 36.Which of these is measured in volts (V)? (a) current (b) resistance (c) voltage (d) power
37. 37.📏 How many milliamperes (mA) make 1 ampere? (a) 1000 (b) 10 (c) 60 (d) 100
38. 38.⚡ A 0.6 W device works on 6 V. What current does it take (in amperes)? =
39. 39.⚡ A device works on 5 V and takes 1 A. What is its power (in watts)? =
40. 40.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)

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