Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 159 · 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 5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
2. 2.🔺 A current of 1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
4. 4.Which of these saves electricity? (a) leave the TV on standby (b) use old filament bulbs (c) run fans in empty rooms (d) unplug idle chargers
5. 5.⚡ A device works on 24 V and takes 2 A. What is its power (in watts)? =
6. 6.🌈 In the resistor colour code, which number does brown stand for?
7. 7.🧩 Which component is a resistance knob? (a) thermistor (b) fuse (c) diode (d) potentiometer
8. 8.🧮 A 14 V battery is joined to 4 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
9. 9.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 25 % (d) 50 %
10. 10.💡 An LED is joined to a 5 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) may burn out (c) does not light
11. 11.🧮 A 0.7 V battery is joined to 4 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
12. 12.📏 In the water-pipe picture of a circuit, resistance is like … (a) the flow of water (b) the water pressure (c) a bigger tank (d) a narrow pipe
13. 13.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) stay the same (d) smaller
14. 14.True or false: to use old filament bulbs saves electricity. (a) False (b) True
15. 15.🔺 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
16. 16.What does a capacitor do? (a) lets current go one way (b) turns a fan or wheels (c) limits the current (d) stores a little charge
17. 17.🔺 A 12 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
18. 18.🧾 A family uses 120 units of electricity in a month and each unit costs ₹9. What is the bill (in ₹)?
19. 19.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
20. 20.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
21. 21.🧮 A 100 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
22. 22.What does an LDR do? (a) smooths a wobbly supply (b) turns a fan or wheels (c) senses how bright it is (d) senses how hot it is
23. 23.🔺 A current of 40 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
24. 24.⚡ A 0.9 W device works on 9 V. What current does it take (in amperes)? =
25. 25.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = R ÷ V (c) I = V + R (d) I = V × R
26. 26.What does a motor do? (a) boosts a small signal (b) lets current go one way (c) makes things spin (d) smooths a wobbly supply
27. 27.🌈 In the resistor colour code, which number does red stand for?
28. 28.Which of these saves electricity? (a) iron one shirt at a time (b) use old filament bulbs (c) switch off empty rooms (d) run fans in empty rooms
29. 29.💡 An LED is joined to a 12 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) lights up (c) may burn out
30. 30.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
31. 31.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = V × I (d) P = I ÷ V
32. 32.True or false: to leave fridge door open saves electricity. (a) False (b) True
33. 33.⚡ A device works on 6 V and takes 0.1 A. What is its power (in watts)? =
34. 34.⚡ A device works on 24 V and takes 1 A. What is its power (in watts)? =
35. 35.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
36. 36.🌈 A resistor has the colour bands violet, black, red. What is its value (in ohms)?
37. 37.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 63 Ω resistor? (a) violet-orange-black (b) blue-orange-black (c) blue-orange-brown (d) orange-blue-black
38. 38.What does a buzzer do? (a) glows using little power (b) makes a beeping sound (c) limits the current (d) is a resistance knob
39. 39.🔺 A 3 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
40. 40.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True

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