Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 857 · 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.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
2. 2.🔺 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
3. 3.True or false: a fuse stores a little charge. (a) True (b) False
4. 4.Which of these wastes electricity? (a) run fans in empty rooms (b) close the fridge quickly (c) use daylight to read (d) unplug idle chargers
5. 5.📏 Which unit measures energy used each second? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
6. 6.🔺 A 1 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
7. 7.📏 How many kilo-ohms (kΩ) is 5900 Ω? =
8. 8.True or false: the ammeter measures current. (a) False (b) True
9. 9.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
10. 10.What does a resistor do? (a) turns a fan or wheels (b) senses how hot it is (c) limits the current (d) is a resistance knob
11. 11.True or false: a fuse blows if current is high. (a) True (b) False
12. 12.📏 Which unit measures the push of a cell? (a) ampere (A) (b) watt (W) (c) volt (V) (d) ohm (Ω)
13. 13.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
14. 14.🧮 A 6 V battery is joined to 2 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
15. 15.🔺 A 1.6 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
16. 16.🔺 A current of 50 mA flows when 23.5 V is joined across a resistor. What is its resistance (in ohms)?
17. 17.True or false: to use daylight to read saves electricity. (a) True (b) False
18. 18.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
19. 19.🔺 A 12.5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
20. 20.What does a diode do? (a) lets current go one way (b) stores a little charge (c) senses how bright it is (d) glows using little power
21. 21.Which of these saves electricity? (a) leave fridge door open (b) iron one shirt at a time (c) use old filament bulbs (d) use LED lamps
22. 22.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🧩 Which part changes electrical energy into movement? (a) a fuse (b) an LED (c) a motor (d) a resistor
24. 24.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
25. 25.📏 Voltmeter or ammeter: which one measures current? (a) voltmeter (b) ammeter
26. 26.🧾 One “unit” on an electricity bill is … (a) 1 volt (b) 1 ampere (c) 1 watt (d) 1 kilowatt-hour (kWh)
27. 27.📏 How many milliamperes (mA) is 1.57 A?
28. 28.🌈 In the resistor colour code, which number does green stand for?
29. 29.True or false: on an LED, the round-side leg is the anode (+). (a) False (b) True
30. 30.True or false: energy used each second is measured in watts (W). (a) False (b) True
31. 31.🔍 Which is the odd one out? (a) use old filament bulbs (b) leave fridge door open (c) leave the TV on standby (d) close the fridge quickly
32. 32.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
33. 33.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to store charge (d) to limit the current
34. 34.🧩 Which part changes electrical energy into sound? (a) a diode (b) a buzzer (c) a resistor (d) a capacitor
35. 35.🌈 A resistor has the colour bands green, orange, black. What is its value (in ohms)?
36. 36.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 8 hours. How many watt-hours (Wh) are saved?
38. 38.🌈 In the resistor colour code, which number does blue stand for?
39. 39.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
40. 40.⚡ A home appliance on the 230 V mains takes 8 A. What is its power (in watts)?

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