Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 202 · 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.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = I ÷ V (d) R = V + I
2. 2.What does a fuse do? (a) is a resistance knob (b) blows if current is high (c) limits the current (d) smooths a wobbly supply
3. 3.🌈 A resistor has the colour bands yellow, yellow, orange. What is its value (in ohms)?
4. 4.📏 Which unit measures power? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
5. 5.🔺 A current of 1.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
6. 6.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
7. 7.🔺 A current of 10 mA flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
8. 8.🔺 A current of 1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
9. 9.Which of these wastes electricity? (a) leave fridge door open (b) close the fridge quickly (c) switch off empty rooms (d) set the AC to 24 °C
10. 10.📏 How many milliamperes (mA) is 1.61 A?
11. 11.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
12. 12.🔍 Which is the odd one out? (a) run fans in empty rooms (b) switch off empty rooms (c) use LED lamps (d) close the fridge quickly
13. 13.True or false: to switch off empty rooms wastes electricity. (a) True (b) False
14. 14.🧩 Which component has coloured bands? (a) buzzer (b) resistor (c) LED (d) capacitor
15. 15.🧮 Five equal 250 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
16. 16.🔺 A current of 0.25 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
17. 17.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it makes a sound (c) it does not light (d) it lights brighter
18. 18.🔺 A 10 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
19. 19.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
20. 20.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a filament bulb (c) an LED lamp (d) a candle
21. 21.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
22. 22.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
23. 23.Which of these wastes electricity? (a) use LED lamps (b) leave the TV on standby (c) switch off empty rooms (d) unplug idle chargers
24. 24.True or false: current is measured in amperes (A). (a) True (b) False
25. 25.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 ampere (c) 1 watt (d) 1 kilowatt-hour (kWh)
26. 26.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
27. 27.True or false: to iron one shirt at a time wastes electricity. (a) False (b) True
28. 28.What does a motor do? (a) beeps for an alarm (b) is a resistance knob (c) makes a beeping sound (d) turns a fan or wheels
29. 29.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
30. 30.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water tank lid (b) the water pressure (c) the tap handle (d) the pipe colour
31. 31.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
32. 32.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) spin a wheel (d) measure heat
33. 33.⚡ A 9 W device works on 9 V. What current does it take (in amperes)? =
34. 34.🧾 A 50 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
35. 35.🔺 A current of 2.5 A flows when 25 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.Which of these saves electricity? (a) use old filament bulbs (b) leave fridge door open (c) leave the TV on standby (d) close the fridge quickly
37. 37.🌈 In the resistor colour code, which number does orange stand for?
38. 38.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the widest gap (c) any band (d) the gold band
39. 39.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
40. 40.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

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