Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 70 · 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 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🧩 Which component senses how hot it is? (a) thermistor (b) buzzer (c) resistor (d) transistor
3. 3.True or false: the ammeter measures voltage. (a) True (b) False
4. 4.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 10 (b) 1024 (c) 100 (d) 1000
5. 5.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) the one nearest an end (d) any band
6. 6.🌈 In the resistor colour code, which number does brown stand for?
7. 7.True or false: to use old filament bulbs saves electricity. (a) True (b) False
8. 8.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
9. 9.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) stay the same (d) smaller
10. 10.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
11. 11.📏 How many milliamperes (mA) is 2.98 A?
12. 12.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
13. 13.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
14. 14.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
15. 15.🔺 A current of 50 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
16. 16.🧩 Which component is a resistance knob? (a) potentiometer (b) resistor (c) motor (d) LED
17. 17.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
18. 18.🔍 Which is the odd one out? (a) unplug idle chargers (b) switch off empty rooms (c) set the AC to 24 °C (d) leave the TV on standby
19. 19.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
20. 20.Which of these saves electricity? (a) use old filament bulbs (b) leave the TV on standby (c) run fans in empty rooms (d) close the fridge quickly
21. 21.📏 How many watts (W) is 2.6 kW?
22. 22.⚡ A device works on 6 V and takes 0.1 A. What is its power (in watts)? =
23. 23.💡 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
24. 24.True or false: to run fans in empty rooms wastes electricity. (a) False (b) True
25. 25.🌈 A resistor has the colour bands orange, white, brown. What is its value (in ohms)?
26. 26.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
27. 27.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
28. 28.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
29. 29.💡 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) may burn out (b) does not light (c) lights up
30. 30.🔺 A current of 1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
31. 31.🧩 Which part changes electrical energy into movement? (a) a motor (b) an LED (c) a fuse (d) a resistor
32. 32.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4500 Ω resistor? (a) green-yellow-red (b) yellow-green-brown (c) yellow-green-red (d) yellow-green-orange
33. 33.💡 Does it save or waste electricity to set the AC to 24 °C? (a) saves electricity (b) wastes electricity
34. 34.🔺 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
35. 35.🔺 A current of 10 mA flows when 1.2 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🔺 A current of 50 mA flows when 16.5 V is joined across a resistor. What is its resistance (in ohms)?
38. 38.🧮 A 10 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)?
39. 39.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
40. 40.💡 An LED is joined to a 9 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) does not light (c) lights up

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