Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 308 · 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 energy used each second? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
2. 2.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
3. 3.🔺 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
4. 4.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 watt (d) 1 ampere
5. 5.True or false: a capacitor has coloured bands. (a) False (b) True
6. 6.True or false: a motor turns a fan or wheels. (a) False (b) True
7. 7.True or false: to run fans in empty rooms saves electricity. (a) True (b) False
8. 8.🔺 A current of 40 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🧩 A capacitor in a circuit can … (a) measure heat (b) make light (c) store charge briefly (d) spin a wheel
10. 10.🌈 A resistor has the colour bands green, red, orange. What is its value (in ohms)?
11. 11.Which of these wastes electricity? (a) close the fridge quickly (b) run fans in empty rooms (c) use LED lamps (d) unplug idle chargers
12. 12.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
13. 13.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = V ÷ R (c) I = V × R (d) I = R ÷ V
14. 14.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
15. 15.What does a resistor do? (a) smooths a wobbly supply (b) has coloured bands (c) makes a beeping sound (d) turns a fan or wheels
16. 16.📏 Which unit measures resistance? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
17. 17.🌈 Which band is read first on a resistor? (a) the widest gap (b) any band (c) the gold band (d) the one nearest an end
18. 18.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 2100 Ω resistor? (a) brown-red-red (b) red-brown-brown (c) red-brown-red (d) red-brown-orange
19. 19.💡 An LED is joined to a 6 V battery with no 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
20. 20.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
21. 21.🔺 A current of 40 mA flows when 12 V is joined across a resistor. What is its resistance (in ohms)?
22. 22.🧩 Which component senses how hot it is? (a) thermistor (b) transistor (c) potentiometer (d) motor
23. 23.Which of these wastes electricity? (a) close the fridge quickly (b) leave the TV on standby (c) switch off empty rooms (d) set the AC to 24 °C
24. 24.🧮 A 22 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
25. 25.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
26. 26.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it does not light (c) it makes a sound (d) it lights brighter
27. 27.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =
28. 28.🧮 A 1.5 V battery is joined to 3 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
29. 29.🔺 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
30. 30.🧮 Resistors of 100 Ω, 50 Ω, 47 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
31. 31.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) bigger (d) smaller
32. 32.📏 How many watts (W) is 3.4 kW?
33. 33.🔺 An 11.75 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
34. 34.💡 An LED is joined to a 5 V battery through a 220 Ω 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
35. 35.🔺 A current of 40 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🌈 In the resistor colour code, which number does blue stand for?
37. 37.True or false: a resistor is a resistance knob. (a) True (b) False
38. 38.🌈 A resistor has the colour bands red, green, orange. What is its value in kilo-ohms (kΩ)? =
39. 39.🔺 A current of 1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
40. 40.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V + I (d) P = V × I

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