Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 792 · 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 0.5 A. What is its power (in watts)?
2. 2.📏 Which unit measures energy used each second? (a) volt (V) (b) ohm (Ω) (c) watt (W) (d) ampere (A)
3. 3.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
4. 4.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🧮 Resistors of 10 Ω, 20 Ω, 68 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
6. 6.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V ÷ I (c) P = V × I (d) P = V + I
7. 7.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a capacitor (c) a diode (d) a buzzer
8. 8.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🧮 A 3.5 V battery is joined to 2 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
10. 10.💡 Does it save or waste electricity to close the fridge quickly? (a) wastes electricity (b) saves electricity
11. 11.🔺 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
12. 12.⚡ A device works on 9 V and takes 0.2 A. What is its power (in watts)? =
13. 13.Which of these saves electricity? (a) use old filament bulbs (b) leave the TV on standby (c) unplug idle chargers (d) iron one shirt at a time
14. 14.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
15. 15.True or false: a diode lets current go one way. (a) False (b) True
16. 16.🔺 A 0.3 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
17. 17.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
18. 18.🧮 Resistors of 220 Ω, 33 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
19. 19.True or false: to use daylight to read wastes electricity. (a) False (b) True
20. 20.🔺 A current of 2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🌈 A resistor has the colour bands blue, blue, yellow. What is its value in kilo-ohms (kΩ)? =
22. 22.🧮 Resistors of 10 Ω, 220 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
23. 23.🔺 A 2 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
24. 24.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) smaller (c) bigger (d) zero
25. 25.⚡ A device works on 24 V and takes 2 A. What is its power (in watts)? =
26. 26.🔺 A 60 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
27. 27.🧮 A 7 V battery is joined to 2 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
28. 28.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
29. 29.🌈 A resistor has the colour bands green, blue, red. What is its value in kilo-ohms (kΩ)? =
30. 30.🧾 A family uses 60 units of electricity in a month and each unit costs ₹5. What is the bill (in ₹)?
31. 31.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
32. 32.⚡ A device works on 5 V and takes 1.5 A. What is its power (in watts)? =
33. 33.🧾 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?
34. 34.🧮 A 5 V battery is joined to 3 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
35. 35.🔺 A current of 40 mA flows when 12 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.🧮 Two resistors in parallel give a total that is … (a) their sum (b) less than either one (c) more than either one (d) always zero
37. 37.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
38. 38.⚡ A device works on 1.5 V and takes 2 A. What is its power (in watts)? =
39. 39.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) may burn out (c) does not light
40. 40.True or false: a thermistor senses how bright it is. (a) True (b) False

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