Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 534 · 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.🧾 One “unit” on an electricity bill is … (a) 1 kilowatt-hour (kWh) (b) 1 ampere (c) 1 volt (d) 1 watt
2. 2.What does a buzzer do? (a) makes things spin (b) blows if current is high (c) beeps for an alarm (d) glows using little power
3. 3.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
4. 4.⚡ Which formula gives electric power? (a) P = V + I (b) P = V ÷ I (c) P = V × I (d) P = I ÷ V
5. 5.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) stay the same (d) zero
6. 6.🔺 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
7. 7.🧮 Resistors of 150 Ω and 150 Ω are joined in series. What is the total resistance (in ohms)?
8. 8.🔺 A current of 3 A flows when 60 V is joined across a resistor. What is its resistance (in ohms)?
9. 9.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
10. 10.🌈 In the resistor colour code, which number does white stand for?
11. 11.🧮 A 1.6 V battery is joined to 6 Ω and 10 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) a narrow pipe (c) the water pressure (d) a bigger tank
13. 13.📏 Which unit measures current? (a) watt (W) (b) ampere (A) (c) ohm (Ω) (d) volt (V)
14. 14.🧮 Resistors of 150 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
15. 15.📏 Which unit measures the push of a cell? (a) ampere (A) (b) watt (W) (c) ohm (Ω) (d) volt (V)
16. 16.⚡ A device works on 24 V and takes 1.5 A. What is its power (in watts)? =
17. 17.🔺 A current of 1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
18. 18.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
19. 19.⚡ A device works on 9 V and takes 1.5 A. What is its power (in watts)? =
20. 20.Which of these wastes electricity? (a) close the fridge quickly (b) use daylight to read (c) switch off empty rooms (d) run fans in empty rooms
21. 21.🔺 A current of 20 mA flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
22. 22.🌈 A resistor has the colour bands green, blue, orange. What is its value in kilo-ohms (kΩ)? =
23. 23.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
24. 24.📏 How many milliamperes (mA) is 0.37 A?
25. 25.💡 An LED is joined to a 12 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) lights up (c) may burn out
26. 26.What does a potentiometer do? (a) senses how hot it is (b) stores a little charge (c) is a resistance knob (d) beeps for an alarm
27. 27.🔺 A current of 0.2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
28. 28.📏 How many ohms (Ω) is 2.8 kΩ?
29. 29.Which of these saves electricity? (a) run fans in empty rooms (b) iron one shirt at a time (c) use old filament bulbs (d) use LED lamps
30. 30.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
31. 31.🧩 Which component turns a fan or wheels? (a) diode (b) capacitor (c) fuse (d) motor
32. 32.🔺 A current of 0.2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🔺 A current of 10 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
34. 34.🧩 Which part changes electrical energy into sound? (a) a diode (b) a capacitor (c) a resistor (d) a buzzer
35. 35.💡 A red LED uses 2 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
36. 36.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
37. 37.True or false: a thermistor senses how hot it is. (a) True (b) False
38. 38.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
39. 39.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
40. 40.🔺 A current of 1.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?

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