Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 890 · 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 10 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🔺 A current of 0.1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?
4. 4.📏 Which unit measures the push of a cell? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
5. 5.🔍 Which is the odd one out? (a) leave fridge door open (b) run fans in empty rooms (c) iron one shirt at a time (d) use daylight to read
6. 6.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 4 V supply. What current flows (in mA)?
7. 7.🧩 Which component blows if current is high? (a) potentiometer (b) LED (c) fuse (d) motor
8. 8.🧩 A capacitor in a circuit can … (a) store charge briefly (b) measure heat (c) make light (d) spin a wheel
9. 9.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
10. 10.⚡ A 10 W device works on 5 V. What current does it take (in amperes)? =
11. 11.⚡ A device works on 24 V and takes 2 A. What is its power (in watts)? =
12. 12.🔺 A current of 1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
13. 13.⚡ A 15 W device works on 5 V. What current does it take (in amperes)? =
14. 14.🧮 Three equal 75 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
15. 15.🌈 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
16. 16.🔺 A current of 1.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
17. 17.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the pipe colour (c) the water tank lid (d) the water pressure
18. 18.🔺 A current of 1.5 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
19. 19.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 240 Ω resistor? (a) red-yellow-red (b) red-yellow-black (c) red-yellow-brown (d) yellow-red-brown
20. 20.🧮 A 150 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
21. 21.🔍 Which is the odd one out? (a) iron one shirt at a time (b) close the fridge quickly (c) run fans in empty rooms (d) use old filament bulbs
22. 22.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to change its colour (d) to limit the current
23. 23.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
24. 24.🧩 Which component boosts a small signal? (a) resistor (b) transistor (c) capacitor (d) LED
25. 25.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
27. 27.🧩 Which component is a resistance knob? (a) potentiometer (b) capacitor (c) LDR (d) fuse
28. 28.🔺 A 9.4 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
29. 29.⚡ Power tells us … (a) energy used each second (b) the colour of light (c) the size of a cell (d) the length of a wire
30. 30.🔍 Which is the odd one out? (a) leave the TV on standby (b) run fans in empty rooms (c) leave fridge door open (d) use LED lamps
31. 31.🧩 Which component stores a little charge? (a) capacitor (b) transistor (c) LDR (d) LED
32. 32.True or false: a resistor lets current go one way. (a) True (b) False
33. 33.True or false: to close the fridge quickly wastes electricity. (a) False (b) True
34. 34.🌈 A resistor has the colour bands white, white, red. What is its value in kilo-ohms (kΩ)? =
35. 35.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
36. 36.True or false: a resistor limits the current. (a) True (b) False
37. 37.🌈 A resistor has the colour bands brown, white, orange. What is its value (in ohms)?
38. 38.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 8000 Ω resistor? (a) grey-black-brown (b) grey-black-orange (c) white-grey-red (d) grey-black-red
39. 39.Which of these wastes electricity? (a) run fans in empty rooms (b) close the fridge quickly (c) switch off empty rooms (d) set the AC to 24 °C
40. 40.True or false: a thermistor senses how hot it is. (a) False (b) True

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