Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 814 · 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 blue LED uses 3 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
2. 2.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
3. 3.🔺 A current of 0.25 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🧾 A family uses 160 units of electricity in a month and each unit costs ₹9. What is the bill (in ₹)?
5. 5.💡 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) does not light (b) lights up (c) may burn out
6. 6.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
7. 7.⚡ A device works on 3 V and takes 1.5 A. What is its power (in watts)? =
8. 8.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
9. 9.💡 An LED is joined to a 5 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
10. 10.True or false: a diode stores a little charge. (a) False (b) True
11. 11.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = I ÷ V (d) R = V + I
12. 12.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = V ÷ R (d) I = R ÷ V
13. 13.📏 Which unit measures current? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)
14. 14.What does a capacitor do? (a) smooths a wobbly supply (b) boosts a small signal (c) blows if current is high (d) is a resistance knob
15. 15.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
16. 16.🌈 A resistor has the colour bands grey, grey, orange. What is its value in kilo-ohms (kΩ)? =
17. 17.Which of these saves electricity? (a) use daylight to read (b) leave fridge door open (c) leave the TV on standby (d) run fans in empty rooms
18. 18.True or false: the ammeter is joined in series. (a) False (b) True
19. 19.🔺 A current of 25 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
20. 20.🔺 A current of 0.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🧮 Resistors of 20 Ω, 330 Ω, 220 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
22. 22.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 ampere (c) 1 volt (d) 1 kilowatt-hour (kWh)
24. 24.🔺 A 12 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
25. 25.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
26. 26.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🌈 A resistor has the colour bands red, yellow, brown. What is its value (in ohms)?
28. 28.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
29. 29.🔺 A 2.5 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
30. 30.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) gets bigger (c) stays the same (d) becomes zero
31. 31.🧩 Which part changes electrical energy into movement? (a) a motor (b) an LED (c) a resistor (d) a fuse
32. 32.🔺 A current of 0.2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🌈 In the resistor colour code, which number does blue stand for?
34. 34.What does a buzzer do? (a) senses how hot it is (b) turns a fan or wheels (c) stores a little charge (d) beeps for an alarm
35. 35.🌈 A resistor has the colour bands grey, grey, brown. What is its value (in ohms)?
36. 36.🔺 A current of 3 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
37. 37.🔍 Which is the odd one out? (a) unplug idle chargers (b) leave the TV on standby (c) leave fridge door open (d) run fans in empty rooms
38. 38.🔺 A current of 10 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.🔺 A current of 40 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🌈 A resistor has the colour bands red, violet, brown. What is its value (in ohms)?

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