Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 863 · 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 watt (b) 1 volt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
2. 2.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
3. 3.🧩 Which component senses how hot it is? (a) fuse (b) LDR (c) capacitor (d) thermistor
4. 4.🔺 A 1.2 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
5. 5.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = R ÷ V (c) I = V ÷ R (d) I = V + R
6. 6.⚡ A device works on 12 V and takes 1.5 A. What is its power (in watts)? =
7. 7.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
8. 8.🔺 A current of 25 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🔺 A current of 0.25 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
10. 10.🔺 A 1.2 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
11. 11.⚡ A 4.5 W device works on 9 V. What current does it take (in amperes)? =
12. 12.🔺 A current of 25 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🌈 A resistor has the colour bands white, brown, orange. What is its value (in ohms)?
14. 14.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I ÷ R (c) V = I × R (d) V = I + R
15. 15.🔺 A 15 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 0 % (c) 5 % (d) 50 %
17. 17.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) any band (d) the one nearest an end
18. 18.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = I ÷ V (d) P = V ÷ I
19. 19.💡 An LED is joined to a 6 V battery through a 220 Ω 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
20. 20.📏 In the water-pipe picture of a circuit, resistance is like … (a) a bigger tank (b) the flow of water (c) the water pressure (d) a narrow pipe
21. 21.What does a diode do? (a) limits the current (b) lets current go one way (c) blows if current is high (d) boosts a small signal
22. 22.💡 What does LED stand for? (a) light energy dial (b) light-emitting diode (c) large electric dial (d) low energy device
23. 23.🧮 Resistors of 47 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
24. 24.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
25. 25.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
26. 26.True or false: to switch off empty rooms wastes electricity. (a) True (b) False
27. 27.🧩 Which component turns a fan or wheels? (a) motor (b) fuse (c) LED (d) potentiometer
28. 28.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
29. 29.Which of these is measured in ohms (Ω)? (a) the push of a cell (b) voltage (c) energy used each second (d) resistance
30. 30.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the tap handle (c) the water tank lid (d) the pipe colour
31. 31.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) smaller (d) zero
32. 32.⚡ A device works on 1.5 V and takes 1.5 A. What is its power (in watts)? =
33. 33.True or false: to run fans in empty rooms saves electricity. (a) True (b) False
34. 34.True or false: a diode lets current go one way. (a) True (b) False
35. 35.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) more than either one (d) their sum
36. 36.🔺 A current of 25 mA flows when 5.5 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V ÷ I (c) R = I ÷ V (d) R = V × I
38. 38.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
39. 39.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
40. 40.True or false: the voltmeter is joined in series. (a) True (b) False

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