Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 776 · 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 senses how bright it is? (a) thermistor (b) resistor (c) LDR (d) capacitor
2. 2.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) stay the same (d) zero
3. 3.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
4. 4.What does a motor do? (a) has coloured bands (b) turns a fan or wheels (c) boosts a small signal (d) blows if current is high
5. 5.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
6. 6.⚡ A 0.6 W device works on 3 V. What current does it take (in amperes)? =
7. 7.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the water pressure (c) the water tank lid (d) the pipe colour
8. 8.📏 How many ohms (Ω) is 7 kΩ?
9. 9.🧮 Resistors of 47 Ω, 20 Ω, 470 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
10. 10.True or false: a resistor has coloured bands. (a) False (b) True
11. 11.📏 How many kilowatts (kW) is 2750 W? =
12. 12.🧮 Five equal 250 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) gets smaller (c) becomes zero (d) stays the same
14. 14.📏 In the water-pipe picture of a circuit, resistance is like … (a) the flow of water (b) a bigger tank (c) the water pressure (d) a narrow pipe
15. 15.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
16. 16.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to store charge (d) to change its colour
17. 17.🧮 Five equal 500 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.Which of these is measured in watts (W)? (a) power (b) the flow of charge (c) resistance (d) the push of a cell
19. 19.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
20. 20.📏 How many milliamperes (mA) is 0.9 A?
21. 21.🔍 Which is the odd one out? (a) close the fridge quickly (b) use daylight to read (c) switch off empty rooms (d) run fans in empty rooms
22. 22.🧩 Which component lets current go one way? (a) transistor (b) resistor (c) capacitor (d) diode
23. 23.🔺 A current of 0.1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🔺 A current of 0.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🔺 A 3 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
26. 26.🔺 A current of 2.5 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
27. 27.🧾 A 50 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
28. 28.📏 How many amperes (A) is 1690 mA? =
29. 29.🔺 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
30. 30.What does a fuse do? (a) lets current go one way (b) boosts a small signal (c) is a resistance knob (d) blows if current is high
31. 31.🌈 In the resistor colour code, which number does brown stand for?
32. 32.Which of these wastes electricity? (a) close the fridge quickly (b) unplug idle chargers (c) switch off empty rooms (d) run fans in empty rooms
33. 33.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🔍 Which is the odd one out? (a) close the fridge quickly (b) set the AC to 24 °C (c) use LED lamps (d) leave fridge door open
35. 35.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
36. 36.⚡ A 4.5 W device works on 1.5 V. What current does it take (in amperes)? =
37. 37.🧮 Four equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.⚡ A 7.5 W device works on 5 V. What current does it take (in amperes)? =
39. 39.True or false: an LED senses how hot it is. (a) True (b) False
40. 40.🔺 A current of 25 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?

Free electronics lessons, practice and worksheets at talentjr.in/electronics-for-kids