Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 870 · 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 component smooths a wobbly supply? (a) buzzer (b) capacitor (c) thermistor (d) LED
2. 2.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
3. 3.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
4. 4.True or false: the voltmeter measures voltage. (a) True (b) False
5. 5.Which of these saves electricity? (a) leave fridge door open (b) close the fridge quickly (c) run fans in empty rooms (d) leave the TV on standby
6. 6.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
8. 8.🧩 Which component makes things spin? (a) transistor (b) motor (c) potentiometer (d) resistor
9. 9.📏 How many milliamperes (mA) is 0.53 A?
10. 10.Which of these saves electricity? (a) use old filament bulbs (b) iron one shirt at a time (c) leave fridge door open (d) set the AC to 24 °C
11. 11.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 kilowatt-hour (kWh) (c) 1 ampere (d) 1 volt
12. 12.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
13. 13.What does an LDR do? (a) senses how bright it is (b) boosts a small signal (c) blows if current is high (d) senses how hot it is
14. 14.💡 An LED is joined to a 5 V battery through a 470 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) may burn out (b) does not light (c) lights up
15. 15.What does a transistor do? (a) turns a fan or wheels (b) boosts a small signal (c) makes a beeping sound (d) limits the current
16. 16.🧾 A family uses 50 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
17. 17.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I ÷ R (c) V = R ÷ I (d) V = I × R
18. 18.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
19. 19.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a candle (c) a filament bulb (d) an oil lamp
20. 20.🔺 A current of 40 mA flows when 16 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.🔺 A 1.2 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
22. 22.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 1 hour. How many watt-hours (Wh) are saved?
23. 23.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 26 Ω resistor? (a) red-blue-black (b) blue-red-black (c) red-blue-brown (d) orange-blue-black
24. 24.🧮 A 1 V battery is joined to 6 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
25. 25.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = I ÷ V (d) P = V ÷ I
26. 26.🧮 Four equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.Which of these is measured in watts (W)? (a) voltage (b) how much a part resists (c) the push of a cell (d) energy used each second
28. 28.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
29. 29.🔍 Which is the odd one out? (a) leave the TV on standby (b) use daylight to read (c) run fans in empty rooms (d) iron one shirt at a time
30. 30.🔺 A current of 3 A flows when 24 V is joined across a resistor. What is its resistance (in ohms)?
31. 31.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 100 (c) 10 (d) 1000
32. 32.🧮 A 15 V battery is joined to 10 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
33. 33.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it lights brighter (c) it does not light (d) it changes colour
34. 34.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
35. 35.🌈 In the resistor colour code, which number does white stand for?
36. 36.🧮 A 330 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)?
37. 37.🧾 A family uses 170 units of electricity in a month and each unit costs ₹9. What is the bill (in ₹)?
38. 38.📏 How many kilo-ohms (kΩ) is 3500 Ω? =
39. 39.🧩 Which component lets current go one way? (a) diode (b) buzzer (c) LDR (d) resistor
40. 40.📏 How many ohms (Ω) is 4.6 kΩ?

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