Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 446 · 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.💡 What happens if an LED is put in backwards? (a) it does not light (b) it makes a sound (c) it changes colour (d) it lights brighter
2. 2.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V + I (d) P = V ÷ I
3. 3.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a filament bulb (c) a candle (d) an oil lamp
4. 4.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
5. 5.🧩 Which component stores a little charge? (a) buzzer (b) capacitor (c) motor (d) LDR
6. 6.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a capacitor (c) a diode (d) a resistor
7. 7.🌈 In the resistor colour code, which number does green stand for?
8. 8.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
9. 9.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = I ÷ V (c) R = V ÷ I (d) R = V × I
10. 10.🔺 A current of 3 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
11. 11.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
12. 12.⚡ A device works on 5 V and takes 1 A. What is its power (in watts)? =
13. 13.🌈 A resistor has the colour bands red, green, orange. What is its value (in ohms)?
14. 14.🧩 Which component boosts a small signal? (a) fuse (b) thermistor (c) diode (d) transistor
15. 15.🔺 A 2.5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
16. 16.🔺 A current of 0.25 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
17. 17.🔺 A current of 1.5 A flows when 18 V is joined across a resistor. What is its resistance (in ohms)?
18. 18.What does a transistor do? (a) makes things spin (b) smooths a wobbly supply (c) limits the current (d) boosts a small signal
19. 19.📏 How many ohms (Ω) is 0.9 kΩ?
20. 20.🧮 A 2.6 V battery is joined to 10 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
21. 21.🔺 A current of 3 A flows when 30 V is joined across a resistor. What is its resistance (in ohms)?
22. 22.Which of these wastes electricity? (a) close the fridge quickly (b) use old filament bulbs (c) set the AC to 24 °C (d) use LED lamps
23. 23.🌈 A resistor has the colour bands red, green, brown. What is its value (in ohms)?
24. 24.🔺 A current of 0.25 A flows when 1.25 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🧮 Five equal 250 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 3 V supply. What current flows (in mA)?
28. 28.📏 How many amperes (A) is 1870 mA? =
29. 29.🧮 A 3.25 V battery is joined to 8 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
30. 30.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
31. 31.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 40 Ω resistor? (a) yellow-black-brown (b) green-yellow-black (c) yellow-black-black (d) green-black-black
32. 32.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
33. 33.💡 An LED is joined to a 5 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) lights up (c) does not light
34. 34.🔍 Which is the odd one out? (a) close the fridge quickly (b) switch off empty rooms (c) use daylight to read (d) run fans in empty rooms
35. 35.🌈 A resistor has the colour bands green, blue, orange. What is its value (in ohms)?
36. 36.🔺 A 24 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
37. 37.What does an LED do? (a) senses how bright it is (b) smooths a wobbly supply (c) lets current go one way (d) glows using little power
38. 38.📏 How many watts (W) is 4.3 kW?
39. 39.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets smaller (c) becomes zero (d) gets bigger
40. 40.🔺 A 2.2 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?

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