Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 100 · 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 of these wastes electricity? (a) use daylight to read (b) set the AC to 24 °C (c) switch off empty rooms (d) leave fridge door open
2. 2.Which of these is measured in amperes (A)? (a) resistance (b) power (c) how much a part resists (d) current
3. 3.🔺 A current of 2.5 A flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
4. 4.🌈 A resistor has the colour bands green, red, orange. What is its value (in ohms)?
5. 5.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a resistor (c) a diode (d) a capacitor
6. 6.🔺 A current of 0.2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 volt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
8. 8.🔺 A current of 2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🔺 A current of 10 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
10. 10.🔺 A 2 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
11. 11.📏 Which unit measures voltage? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
12. 12.🧮 A 1 V battery is joined to 2 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
13. 13.📏 Which unit measures the push of a cell? (a) volt (V) (b) ampere (A) (c) watt (W) (d) ohm (Ω)
14. 14.True or false: to set the AC to 24 °C saves electricity. (a) True (b) False
15. 15.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it does not light (c) it makes a sound (d) it changes colour
16. 16.🧮 Resistors of 220 Ω, 150 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
17. 17.🔺 A current of 50 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
18. 18.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
19. 19.🔺 A 1.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
20. 20.🌈 A resistor has the colour bands orange, black, orange. What is its value (in ohms)?
21. 21.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
22. 22.🧩 Which component senses how bright it is? (a) motor (b) potentiometer (c) LDR (d) resistor
23. 23.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
24. 24.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🔺 An 8.25 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
26. 26.🧮 Resistors of 220 Ω, 470 Ω, 50 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
27. 27.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
28. 28.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) bigger (d) zero
29. 29.🔺 A 16 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
30. 30.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = V + I (d) R = I ÷ V
31. 31.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to make it brighter (d) to limit the current
32. 32.🧩 Which component beeps for an alarm? (a) diode (b) buzzer (c) capacitor (d) thermistor
33. 33.True or false: to iron one shirt at a time saves electricity. (a) True (b) False
34. 34.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
35. 35.Which of these saves electricity? (a) close the fridge quickly (b) use old filament bulbs (c) iron one shirt at a time (d) run fans in empty rooms
36. 36.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
37. 37.True or false: a motor turns a fan or wheels. (a) False (b) True
38. 38.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
39. 39.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
40. 40.🔺 A current of 0.2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =

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