Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 502 · 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.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
2. 2.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a buzzer (c) a capacitor (d) a diode
3. 3.True or false: power is measured in ohms (Ω). (a) False (b) True
4. 4.🧮 A 10 V battery is joined to 6 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
5. 5.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
6. 6.Which of these is measured in watts (W)? (a) the push of a cell (b) power (c) the flow of charge (d) voltage
7. 7.🔺 A current of 10 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
8. 8.Which of these wastes electricity? (a) use LED lamps (b) switch off empty rooms (c) set the AC to 24 °C (d) leave the TV on standby
9. 9.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
10. 10.🧩 Which part changes electrical energy into movement? (a) a fuse (b) a motor (c) a resistor (d) an LED
11. 11.🔍 Which is the odd one out? (a) run fans in empty rooms (b) set the AC to 24 °C (c) use LED lamps (d) switch off empty rooms
12. 12.🔍 Which is the odd one out? (a) leave the TV on standby (b) unplug idle chargers (c) close the fridge quickly (d) switch off empty rooms
13. 13.📏 How many amperes (A) is 30 mA? =
14. 14.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 0 % (c) 50 % (d) 5 %
15. 15.🧮 An 8 V battery is joined to 4 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
16. 16.🧩 A capacitor in a circuit can … (a) spin a wheel (b) store charge briefly (c) measure heat (d) make light
17. 17.🔺 A current of 25 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
18. 18.🔍 Which is the odd one out? (a) use LED lamps (b) iron one shirt at a time (c) switch off empty rooms (d) set the AC to 24 °C
19. 19.🧮 Resistors of 150 Ω, 22 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
20. 20.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
21. 21.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
22. 22.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
23. 23.True or false: an LDR stores a little charge. (a) True (b) False
24. 24.True or false: a capacitor stores a little charge. (a) False (b) True
25. 25.🧾 A 500 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
26. 26.Which of these is measured in ohms (Ω)? (a) power (b) energy used each second (c) resistance (d) current
27. 27.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
28. 28.🧩 Which component lets current go one way? (a) fuse (b) diode (c) resistor (d) motor
29. 29.True or false: on an LED, the round-side leg is the anode (+). (a) True (b) False
30. 30.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 900 Ω resistor? (a) white-black-brown (b) brown-white-brown (c) white-black-black (d) white-black-red
31. 31.🔺 A current of 50 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
32. 32.⚡ A device works on 1.5 V and takes 0.2 A. What is its power (in watts)? =
33. 33.⚡ Power tells us … (a) energy used each second (b) the length of a wire (c) the colour of light (d) the size of a cell
34. 34.📏 How many kilo-ohms (kΩ) is 4700 Ω? =
35. 35.Which of these saves electricity? (a) leave the TV on standby (b) iron one shirt at a time (c) run fans in empty rooms (d) unplug idle chargers
36. 36.🧩 Which component smooths a wobbly supply? (a) diode (b) transistor (c) LDR (d) capacitor
37. 37.🔺 A 3 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
38. 38.🔺 A current of 50 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.🔺 A current of 20 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.🔺 A 10 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =

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