Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 167 · 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 2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
2. 2.💡 Why does an LED need a resistor in series? (a) to store charge (b) to change its colour (c) to limit the current (d) to make it brighter
3. 3.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
4. 4.📏 How many amperes (A) is 1330 mA? =
5. 5.🔺 A 4.7 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
6. 6.True or false: a transistor boosts a small signal. (a) True (b) False
7. 7.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
8. 8.🔺 A current of 50 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🧮 Four equal 80 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
10. 10.🌈 In the resistor colour code, which number does orange stand for?
11. 11.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an LED lamp (c) a candle (d) an oil lamp
12. 12.Which of these saves electricity? (a) use old filament bulbs (b) leave fridge door open (c) run fans in empty rooms (d) switch off empty rooms
13. 13.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
14. 14.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
15. 15.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
16. 16.True or false: an LED limits the current. (a) True (b) False
17. 17.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
18. 18.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
19. 19.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) energy used each second (d) the length of a wire
20. 20.What does a capacitor do? (a) beeps for an alarm (b) boosts a small signal (c) senses how hot it is (d) smooths a wobbly supply
21. 21.🌈 A resistor has the colour bands blue, white, red. What is its value in kilo-ohms (kΩ)? =
22. 22.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
23. 23.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
24. 24.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it does not light (c) it changes colour (d) it makes a sound
25. 25.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 volt (c) 1 watt (d) 1 ampere
26. 26.🔺 A current of 0.1 A flows when 0.3 V is joined across a resistor. What is its resistance (in ohms)?
27. 27.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the gold band (d) the widest gap
28. 28.🔺 A current of 0.1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
29. 29.🔺 A current of 0.2 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
31. 31.True or false: energy used each second is measured in watts (W). (a) True (b) False
32. 32.🔍 Which is the odd one out? (a) run fans in empty rooms (b) use LED lamps (c) leave the TV on standby (d) leave fridge door open
33. 33.What does a transistor do? (a) blows if current is high (b) senses how bright it is (c) boosts a small signal (d) beeps for an alarm
34. 34.💡 Does it save or waste electricity to set the AC to 24 °C? (a) saves electricity (b) wastes electricity
35. 35.Which of these wastes electricity? (a) use daylight to read (b) switch off empty rooms (c) close the fridge quickly (d) leave fridge door open
36. 36.Which of these is measured in amperes (A)? (a) the push of a cell (b) power (c) current (d) resistance
37. 37.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
38. 38.💡 A red LED uses 2 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
39. 39.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity
40. 40.Which of these wastes electricity? (a) close the fridge quickly (b) leave the TV on standby (c) use daylight to read (d) use LED lamps

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