Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 962 · 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 I? (a) I = V × R (b) I = R ÷ V (c) I = V + R (d) I = V ÷ R
2. 2.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the length of a wire (d) the size of a cell
3. 3.🔺 A current of 20 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🧩 Which component beeps for an alarm? (a) buzzer (b) motor (c) diode (d) capacitor
5. 5.True or false: voltage is measured in volts (V). (a) False (b) True
6. 6.🔺 A current of 2 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
7. 7.⚡ A device works on 9 V and takes 1.5 A. What is its power (in watts)? =
8. 8.💡 A red LED uses 2 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
9. 9.🧮 A 33 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
10. 10.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
11. 11.True or false: to switch off empty rooms wastes electricity. (a) True (b) False
12. 12.🧮 Resistors of 33 Ω, 470 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
13. 13.🧩 Which component senses how bright it is? (a) LED (b) LDR (c) potentiometer (d) thermistor
14. 14.What does a potentiometer do? (a) boosts a small signal (b) is a resistance knob (c) senses how hot it is (d) has coloured bands
15. 15.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
16. 16.True or false: on an LED, the round-side leg is the anode (+). (a) False (b) True
17. 17.⚡ A device works on 1.5 V and takes 3 A. What is its power (in watts)? =
18. 18.True or false: a potentiometer has coloured bands. (a) False (b) True
19. 19.True or false: a buzzer makes a beeping sound. (a) False (b) True
20. 20.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 0 % (c) 25 % (d) 5 %
21. 21.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = V + I (d) P = I ÷ V
22. 22.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
23. 23.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the flow of water (c) a bigger tank (d) the water pressure
24. 24.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
25. 25.True or false: to use daylight to read saves electricity. (a) False (b) True
26. 26.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) stay the same (d) smaller
27. 27.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
28. 28.🧮 Resistors of 22 Ω, 10 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
29. 29.🔍 Which is the odd one out? (a) switch off empty rooms (b) use LED lamps (c) close the fridge quickly (d) leave fridge door open
30. 30.🌈 A resistor has the colour bands blue, green, yellow. What is its value in kilo-ohms (kΩ)? =
31. 31.💡 An LED is joined to a 9 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
32. 32.⚡ A device works on 24 V and takes 3 A. What is its power (in watts)? =
33. 33.📏 Which unit measures the flow of charge? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
34. 34.🌈 In the resistor colour code, which number does blue stand for?
35. 35.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
36. 36.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
37. 37.📏 Which unit measures resistance? (a) ampere (A) (b) ohm (Ω) (c) watt (W) (d) volt (V)
38. 38.True or false: the ammeter is joined across a part. (a) True (b) False
39. 39.🧩 Which component smooths a wobbly supply? (a) thermistor (b) capacitor (c) diode (d) buzzer
40. 40.🔺 A current of 50 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?

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