Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 237 · 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.🔺 A current of 25 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
2. 2.🌈 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
3. 3.📏 Which unit measures voltage? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
4. 4.True or false: a fuse beeps for an alarm. (a) True (b) False
5. 5.True or false: the voltmeter is joined in series. (a) True (b) False
6. 6.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
7. 7.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 4 hours. How many watt-hours (Wh) are saved?
8. 8.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 0 % (d) 25 %
9. 9.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
10. 10.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
11. 11.🔺 A current of 20 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
12. 12.🧩 Which component has coloured bands? (a) diode (b) fuse (c) resistor (d) LED
13. 13.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 92 Ω resistor? (a) brown-red-black (b) white-red-black (c) white-red-brown (d) red-white-black
14. 14.🧮 Resistors of 22 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
15. 15.🔺 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
16. 16.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
17. 17.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) energy used each second (d) the size of a cell
18. 18.🔺 A 2.2 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
19. 19.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = I ÷ V (d) P = V × I
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 30 Ω resistor? (a) yellow-orange-black (b) orange-black-brown (c) yellow-black-black (d) orange-black-black
21. 21.🔺 A current of 40 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
22. 22.True or false: a fuse blows if current is high. (a) True (b) False
23. 23.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to limit the current (d) to store charge
24. 24.📏 Which unit measures current? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
25. 25.🧮 Two resistors in parallel give a total that is … (a) always zero (b) their sum (c) more than either one (d) less than either one
26. 26.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
27. 27.🔺 A current of 2 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.🧩 Which part changes electrical energy into movement? (a) a fuse (b) an LED (c) a motor (d) a resistor
29. 29.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
30. 30.💡 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)?
31. 31.⚡ A 2.5 W device works on 5 V. What current does it take (in amperes)? =
32. 32.💡 An LED is joined to a 6 V battery through a 220 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) does not light (b) lights up (c) may burn out
33. 33.📏 How many ohms (Ω) is 3.2 kΩ?
34. 34.⚡ A 1.5 W device works on 6 V. What current does it take (in amperes)? =
35. 35.🧩 A capacitor in a circuit can … (a) measure heat (b) make light (c) spin a wheel (d) store charge briefly
36. 36.🔺 A 10 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
37. 37.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = V ÷ R (c) I = R ÷ V (d) I = V × R
38. 38.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) the flow of water (c) a bigger tank (d) a narrow pipe
39. 39.Which of these is measured in watts (W)? (a) how much a part resists (b) power (c) the push of a cell (d) resistance
40. 40.🧮 A 220 Ω resistor is joined in series with two equal 200 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?

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