Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 720 · 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 formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = V × I (d) P = I ÷ V
2. 2.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🧾 A family uses 70 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
4. 4.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
5. 5.🌈 A resistor has the colour bands red, red, brown. What is its value (in ohms)?
6. 6.🌈 A resistor has the colour bands violet, violet, black. What is its value (in ohms)?
7. 7.🔺 A current of 25 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
8. 8.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 6 V supply. What current flows (in mA)?
9. 9.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it changes colour (c) it makes a sound (d) it does not light
10. 10.💡 Does it save or waste electricity to run fans in empty rooms? (a) wastes electricity (b) saves electricity
11. 11.🧩 A capacitor in a circuit can … (a) measure heat (b) spin a wheel (c) store charge briefly (d) make light
12. 12.🧾 A family uses 190 units of electricity in a month and each unit costs ₹8. What is the bill (in ₹)?
13. 13.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 50 % (c) 25 % (d) 5 %
14. 14.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) always zero (d) less than either one
15. 15.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) stay the same (c) zero (d) smaller
16. 16.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🌈 In the resistor colour code, which number does green stand for?
18. 18.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
19. 19.📏 How many kilowatts (kW) is 1300 W? =
20. 20.⚡ A device works on 12 V and takes 0.2 A. What is its power (in watts)? =
21. 21.🔺 A current of 50 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🌈 A resistor has the colour bands orange, violet, red. What is its value in kilo-ohms (kΩ)? =
23. 23.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 volt (c) 1 kilowatt-hour (kWh) (d) 1 ampere
24. 24.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
25. 25.🧩 Which component senses how bright it is? (a) LED (b) potentiometer (c) fuse (d) LDR
26. 26.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) gets smaller (d) becomes zero
27. 27.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a filament bulb (c) an LED lamp (d) a candle
28. 28.True or false: a thermistor senses how hot it is. (a) True (b) False
29. 29.True or false: voltage is measured in watts (W). (a) False (b) True
30. 30.🧮 Three equal 150 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
31. 31.🔺 A current of 20 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.💡 Why does an LED need a resistor in series? (a) to store charge (b) to limit the current (c) to make it brighter (d) to change its colour
33. 33.🔺 A current of 25 mA flows when 5.5 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.🧮 A 2.8 V battery is joined to 4 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
35. 35.🌈 A resistor has the colour bands green, white, yellow. What is its value in kilo-ohms (kΩ)? =
36. 36.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
37. 37.What does a thermistor do? (a) turns a fan or wheels (b) boosts a small signal (c) senses how hot it is (d) has coloured bands
38. 38.🧮 Resistors of 20 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
39. 39.Which of these saves electricity? (a) use old filament bulbs (b) iron one shirt at a time (c) leave fridge door open (d) switch off empty rooms
40. 40.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) any band (d) the gold band

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