Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 189 · 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.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V + I (c) R = V ÷ I (d) R = V × I
2. 2.🧩 Which component blows if current is high? (a) motor (b) fuse (c) resistor (d) potentiometer
3. 3.🔺 A current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🧮 Two resistors in parallel give a total that is … (a) less than either one (b) always zero (c) their sum (d) more than either one
5. 5.🔺 A current of 1.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
6. 6.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
7. 7.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
8. 8.True or false: to use old filament bulbs wastes electricity. (a) True (b) False
9. 9.🌈 Which band is read first on a resistor? (a) any band (b) the widest gap (c) the one nearest an end (d) the gold band
10. 10.🔺 A current of 0.1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
11. 11.🧾 A 500 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
12. 12.True or false: an LED senses how hot it is. (a) True (b) False
13. 13.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
14. 14.🔺 A current of 40 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.True or false: the ammeter measures current. (a) True (b) False
16. 16.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
17. 17.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V + I (d) P = V ÷ I
18. 18.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
19. 19.🧩 Which component senses how bright it is? (a) LDR (b) buzzer (c) transistor (d) thermistor
20. 20.Which of these wastes electricity? (a) use daylight to read (b) switch off empty rooms (c) use LED lamps (d) leave fridge door open
21. 21.🔺 A 4 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
22. 22.🔺 A current of 0.1 A flows when 0.5 V is joined across a resistor. What is its resistance (in ohms)?
23. 23.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) smaller (c) zero (d) bigger
24. 24.Which of these is measured in amperes (A)? (a) the flow of charge (b) voltage (c) the push of a cell (d) how much a part resists
25. 25.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🔺 A current of 40 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
27. 27.📏 How many kilo-ohms (kΩ) is 9400 Ω? =
28. 28.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
29. 29.True or false: an LED smooths a wobbly supply. (a) False (b) True
30. 30.🔺 A 10 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
31. 31.🔺 A current of 0.25 A flows when 0.75 V is joined across a resistor. What is its resistance (in ohms)?
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 home appliance on the 230 V mains takes 8 A. What is its power (in watts)?
34. 34.💡 What does LED stand for? (a) light energy dial (b) large electric dial (c) light-emitting diode (d) low energy device
35. 35.🧩 Which component has coloured bands? (a) transistor (b) fuse (c) resistor (d) buzzer
36. 36.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
37. 37.🧮 Two equal 220 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to change its colour (c) to store charge (d) to make it brighter
39. 39.🔺 A current of 0.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🔍 Which is the odd one out? (a) switch off empty rooms (b) use old filament bulbs (c) leave the TV on standby (d) iron one shirt at a time

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