Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 265 · 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.What does a resistor do? (a) lets current go one way (b) senses how bright it is (c) limits the current (d) turns a fan or wheels
2. 2.🔺 A current of 0.1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
3. 3.📏 Which unit measures energy used each second? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
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.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
6. 6.🧩 Which component smooths a wobbly supply? (a) capacitor (b) resistor (c) buzzer (d) transistor
7. 7.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
8. 8.🔺 A current of 0.2 A flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
9. 9.💡 Why does an LED need a resistor in series? (a) to store charge (b) to limit the current (c) to change its colour (d) to make it brighter
10. 10.💡 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?
11. 11.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
12. 12.🌈 In the resistor colour code, which number does green stand for?
13. 13.🌈 A resistor has the colour bands violet, orange, black. What is its value (in ohms)?
14. 14.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a diode (c) a buzzer (d) a capacitor
15. 15.💡 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
16. 16.🔺 A current of 10 mA flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
17. 17.🔺 A current of 50 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
18. 18.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 5 V supply. What current flows (in mA)?
19. 19.Which of these is measured in amperes (A)? (a) the flow of charge (b) voltage (c) resistance (d) power
20. 20.Which of these is measured in volts (V)? (a) energy used each second (b) the flow of charge (c) current (d) the push of a cell
21. 21.🔺 A 24 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
22. 22.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the gold band (c) the widest gap (d) any band
23. 23.🧩 Which component beeps for an alarm? (a) motor (b) resistor (c) buzzer (d) diode
24. 24.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
25. 25.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) use LED lamps (c) iron one shirt at a time (d) unplug idle chargers
27. 27.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
28. 28.What does a fuse do? (a) stores a little charge (b) senses how bright it is (c) makes a beeping sound (d) blows if current is high
29. 29.🌈 A resistor has the colour bands white, blue, black. What is its value (in ohms)?
30. 30.🌈 In the resistor colour code, which number does black stand for?
31. 31.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
32. 32.True or false: the voltmeter measures voltage. (a) False (b) True
33. 33.🔺 A 1 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
34. 34.🌈 A resistor has the colour bands white, violet, black. What is its value (in ohms)?
35. 35.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 6 V supply. What current flows (in mA)?
36. 36.⚡ A 9 W device works on 6 V. What current does it take (in amperes)? =
37. 37.True or false: to switch off empty rooms saves electricity. (a) False (b) True
38. 38.🧮 Resistors of 100 Ω, 20 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
39. 39.Which of these saves electricity? (a) use daylight to read (b) leave fridge door open (c) leave the TV on standby (d) run fans in empty rooms
40. 40.🔺 A 5 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =

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