Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 553 · 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.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
2. 2.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
3. 3.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🔺 An 8.25 V supply is joined across a 330 Ω resistor. What current flows (in milliamperes, mA)?
5. 5.🧮 A 470 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
6. 6.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
7. 7.💡 An LED is joined to a 6 V battery through a 470 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) does not light (b) lights up (c) may burn out
8. 8.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
9. 9.True or false: the ammeter is joined in series. (a) True (b) False
10. 10.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 1000 (c) 10 (d) 100
11. 11.🧩 Which part changes electrical energy into movement? (a) a motor (b) an LED (c) a fuse (d) a resistor
12. 12.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
13. 13.Which of these is measured in amperes (A)? (a) energy used each second (b) the push of a cell (c) the flow of charge (d) power
14. 14.🧮 A 10 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)?
15. 15.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
16. 16.🔺 A 22.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
17. 17.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
18. 18.🔺 A 1 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
19. 19.🧮 Four equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
20. 20.🔺 A 2 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
21. 21.True or false: voltage is measured in ohms (Ω). (a) False (b) True
22. 22.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) any band (c) the widest gap (d) the gold band
23. 23.📏 Which unit measures power? (a) watt (W) (b) ampere (A) (c) volt (V) (d) ohm (Ω)
24. 24.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
25. 25.🔺 A current of 25 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
26. 26.📏 Which unit measures how much a part resists? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
27. 27.⚡ An 18 W device works on 9 V. What current does it take (in amperes)? =
28. 28.True or false: to iron one shirt at a time saves electricity. (a) False (b) True
29. 29.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 2 hours. How many watt-hours (Wh) are saved?
30. 30.What does a buzzer do? (a) glows using little power (b) turns a fan or wheels (c) beeps for an alarm (d) stores a little charge
31. 31.🌈 A resistor has the colour bands blue, brown, red. What is its value in kilo-ohms (kΩ)? =
32. 32.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a buzzer (c) a diode (d) a capacitor
33. 33.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
34. 34.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = I + R (c) V = R ÷ I (d) V = I ÷ R
35. 35.🔺 A current of 2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) energy used each second (d) the size of a cell
38. 38.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
40. 40.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)

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