Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 573 · 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.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
2. 2.True or false: a thermistor limits the current. (a) False (b) True
3. 3.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 370 Ω resistor? (a) orange-violet-black (b) orange-violet-brown (c) orange-violet-red (d) violet-orange-brown
4. 4.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) an LED lamp (c) a filament bulb (d) a candle
5. 5.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to limit the current (d) to make it brighter
6. 6.What does a transistor do? (a) boosts a small signal (b) is a resistance knob (c) blows if current is high (d) turns a fan or wheels
7. 7.📏 In the water-pipe picture of a circuit, current is like … (a) the pipe colour (b) the water pressure (c) the flow of water (d) a narrow pipe
8. 8.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
9. 9.🌈 A resistor has the colour bands grey, brown, red. What is its value (in ohms)?
10. 10.True or false: an LDR turns a fan or wheels. (a) True (b) False
11. 11.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) less than either one (d) their sum
12. 12.💡 An LED is joined to a 3 V battery through a 220 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) lights up (b) does not light (c) may burn out
13. 13.🌈 In the resistor colour code, which number does brown stand for?
14. 14.🌈 A resistor has the colour bands yellow, red, orange. What is its value in kilo-ohms (kΩ)? =
15. 15.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 watt (c) 1 ampere (d) 1 volt
16. 16.🌈 A resistor has the colour bands grey, violet, red. What is its value in kilo-ohms (kΩ)? =
17. 17.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
18. 18.🌈 Which band is read first on a resistor? (a) the gold band (b) any band (c) the widest gap (d) the one nearest an end
19. 19.⚡ A device works on 5 V and takes 0.25 A. What is its power (in watts)? =
20. 20.🧮 Five equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
21. 21.🧮 Resistors of 220 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
22. 22.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
23. 23.Which of these wastes electricity? (a) unplug idle chargers (b) set the AC to 24 °C (c) leave fridge door open (d) switch off empty rooms
24. 24.⚡ A device works on 6 V and takes 2 A. What is its power (in watts)? =
25. 25.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
26. 26.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
27. 27.🔺 A current of 20 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
28. 28.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
29. 29.Which of these is measured in amperes (A)? (a) resistance (b) voltage (c) power (d) current
30. 30.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
31. 31.🔍 Which is the odd one out? (a) leave the TV on standby (b) use LED lamps (c) unplug idle chargers (d) set the AC to 24 °C
32. 32.True or false: an LDR senses how bright it is. (a) True (b) False
33. 33.🧩 Which component blows if current is high? (a) fuse (b) LED (c) transistor (d) LDR
34. 34.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
35. 35.🧩 Which component stores a little charge? (a) capacitor (b) potentiometer (c) diode (d) thermistor
36. 36.Which of these is measured in watts (W)? (a) the flow of charge (b) energy used each second (c) voltage (d) how much a part resists
37. 37.True or false: current is measured in amperes (A). (a) True (b) False
38. 38.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
39. 39.🔺 A 5 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
40. 40.🔺 An 8 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?

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