Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 848 · 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 home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
2. 2.💡 Does it save or waste electricity to use old filament bulbs? (a) wastes electricity (b) saves electricity
3. 3.🧩 Which component stores a little charge? (a) fuse (b) LDR (c) transistor (d) capacitor
4. 4.🔍 Which is the odd one out? (a) run fans in empty rooms (b) iron one shirt at a time (c) leave the TV on standby (d) unplug idle chargers
5. 5.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 watt (c) 1 ampere (d) 1 volt
6. 6.🧩 Which component beeps for an alarm? (a) motor (b) capacitor (c) buzzer (d) potentiometer
7. 7.📏 How many watts (W) is 0.4 kW?
8. 8.🔺 A current of 0.2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🔺 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
10. 10.True or false: a capacitor stores a little charge. (a) True (b) False
11. 11.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
12. 12.⚡ A 12 W device works on 24 V. What current does it take (in amperes)? =
13. 13.What does a potentiometer do? (a) is a resistance knob (b) senses how hot it is (c) stores a little charge (d) smooths a wobbly supply
14. 14.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
15. 15.📏 How many watts (W) is 3.2 kW?
16. 16.🧾 A family uses 180 units of electricity in a month and each unit costs ₹7. What is the bill (in ₹)?
17. 17.🌈 A resistor has the colour bands orange, red, red. What is its value in kilo-ohms (kΩ)? =
18. 18.🔺 A current of 10 mA flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
19. 19.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
20. 20.💡 What does LED stand for? (a) large electric dial (b) low energy device (c) light-emitting diode (d) light energy dial
21. 21.🔺 A 24 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
22. 22.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to change its colour (d) to limit the current
23. 23.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) more than either one (c) their sum (d) always zero
24. 24.🔺 A current of 0.2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🧩 Which part changes electrical energy into movement? (a) a resistor (b) an LED (c) a motor (d) a fuse
26. 26.🔺 A 20 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
27. 27.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?
28. 28.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
29. 29.🧮 Resistors of 47 Ω, 47 Ω, 22 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
30. 30.🧮 Four equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
31. 31.🔺 A current of 2 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
33. 33.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an oil lamp (d) an LED lamp
35. 35.🔺 A current of 2 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
36. 36.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
37. 37.🔺 A current of 1.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
38. 38.💡 What happens if an LED is put in backwards? (a) it does not light (b) it makes a sound (c) it lights brighter (d) it changes colour
39. 39.🧮 A 47 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
40. 40.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)

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