Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 785 · 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.🌈 In the resistor colour code, which number does red stand for?
2. 2.🧾 A 50 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
3. 3.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = R ÷ I (c) V = I ÷ R (d) V = I × R
4. 4.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
5. 5.True or false: power is measured in watts (W). (a) False (b) True
6. 6.🌈 A resistor has the colour bands blue, green, brown. What is its value (in ohms)?
7. 7.🧾 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
8. 8.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
9. 9.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
10. 10.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
11. 11.🧩 Which part changes electrical energy into movement? (a) an LED (b) a fuse (c) a resistor (d) a motor
12. 12.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 25 % (d) 50 %
13. 13.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it lights brighter (c) it makes a sound (d) it does not light
14. 14.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
15. 15.🔺 A current of 40 mA flows when 18.8 V is joined across a resistor. What is its resistance (in ohms)?
16. 16.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to make it brighter (d) to limit the current
17. 17.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
18. 18.True or false: resistance is measured in amperes (A). (a) True (b) False
19. 19.🔺 A current of 1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
20. 20.What does an LDR do? (a) lets current go one way (b) stores a little charge (c) makes things spin (d) senses how bright it is
21. 21.💡 What does LED stand for? (a) light energy dial (b) low energy device (c) light-emitting diode (d) large electric dial
22. 22.🧮 A 68 Ω resistor is joined in series with two equal 200 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
23. 23.🔺 A current of 0.25 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
24. 24.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
25. 25.Which of these wastes electricity? (a) leave the TV on standby (b) use LED lamps (c) switch off empty rooms (d) close the fridge quickly
26. 26.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V ÷ I (c) R = V × I (d) R = I ÷ V
27. 27.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
28. 28.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 kilowatt-hour (kWh) (c) 1 watt (d) 1 ampere
29. 29.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
30. 30.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
31. 31.🔺 A 7.5 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
32. 32.🔺 A current of 25 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
34. 34.🧩 Which part changes electrical energy into sound? (a) a diode (b) a capacitor (c) a buzzer (d) a resistor
35. 35.🧮 Three equal 150 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
36. 36.True or false: a fuse is a resistance knob. (a) False (b) True
37. 37.🧮 A 33 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
38. 38.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🌈 A resistor has the colour bands violet, brown, brown. What is its value (in ohms)?
40. 40.🧾 A family uses 100 units of electricity in a month and each unit costs ₹6. What is the bill (in ₹)?

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