Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 983 · 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.📏 Voltmeter or ammeter: which one is joined in series? (a) ammeter (b) voltmeter
2. 2.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 25 Ω resistor? (a) orange-green-black (b) red-green-brown (c) red-green-black (d) green-red-black
3. 3.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
4. 4.🔺 A current of 0.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
5. 5.What does a transistor do? (a) senses how hot it is (b) blows if current is high (c) has coloured bands (d) boosts a small signal
6. 6.🌈 A resistor has the colour bands orange, violet, orange. What is its value in kilo-ohms (kΩ)? =
7. 7.🧩 Which part changes electrical energy into sound? (a) a diode (b) a buzzer (c) a resistor (d) a capacitor
8. 8.What does an LED do? (a) has coloured bands (b) stores a little charge (c) lets current go one way (d) glows using little power
9. 9.True or false: current is measured in amperes (A). (a) True (b) False
10. 10.⚡ Power tells us … (a) energy used each second (b) the colour of light (c) the length of a wire (d) the size of a cell
11. 11.⚡ An 18 W device works on 6 V. What current does it take (in amperes)? =
12. 12.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to limit the current (d) to change its colour
13. 13.Which of these is measured in watts (W)? (a) current (b) the push of a cell (c) power (d) the flow of charge
14. 14.True or false: how much a part resists is measured in ohms (Ω). (a) False (b) True
15. 15.🔺 An 8.8 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.🔺 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
17. 17.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
18. 18.💡 Does it save or waste electricity to unplug idle chargers? (a) wastes electricity (b) saves electricity
19. 19.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
20. 20.🔺 A 1.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
21. 21.🔺 A current of 0.25 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
22. 22.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
23. 23.🧩 Which component senses how hot it is? (a) LED (b) diode (c) LDR (d) thermistor
24. 24.📏 Which unit measures current? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
25. 25.🔺 A current of 40 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
26. 26.⚡ An 18 W device works on 12 V. What current does it take (in amperes)? =
27. 27.🔺 A current of 0.2 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
28. 28.True or false: to switch off empty rooms saves electricity. (a) True (b) False
29. 29.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the flow of water (c) the water pressure (d) a bigger tank
30. 30.🧮 A 22 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
31. 31.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
32. 32.🧩 A capacitor in a circuit can … (a) make light (b) measure heat (c) store charge briefly (d) spin a wheel
33. 33.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
34. 34.🔺 A 15 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
35. 35.💡 A red LED uses 2 V and should get 10 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
36. 36.📏 How many watts (W) is 3.4 kW?
37. 37.📏 How many milliamperes (mA) is 0.17 A?
38. 38.🔺 A current of 1.5 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
39. 39.True or false: to leave fridge door open wastes electricity. (a) True (b) False
40. 40.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) stay the same (c) zero (d) smaller

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