Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 803 · 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 = V ÷ R (c) I = V + R (d) I = R ÷ V
2. 2.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 38 Ω resistor? (a) orange-grey-brown (b) yellow-grey-black (c) grey-orange-black (d) orange-grey-black
3. 3.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a capacitor (d) a buzzer
4. 4.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
5. 5.True or false: a resistor has coloured bands. (a) True (b) False
6. 6.🔺 A current of 0.2 A flows when 0.4 V is joined across a resistor. What is its resistance (in ohms)?
7. 7.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
8. 8.🌈 A resistor has the colour bands orange, violet, brown. What is its value (in ohms)?
9. 9.📏 How many kilo-ohms (kΩ) is 1400 Ω? =
10. 10.🔺 A current of 0.1 A flows when 0.2 V is joined across a resistor. What is its resistance (in ohms)?
11. 11.🌈 Which band is read first on a resistor? (a) the gold band (b) any band (c) the widest gap (d) the one nearest an end
12. 12.🧮 A 3.75 V battery is joined to 10 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
13. 13.Which of these saves electricity? (a) leave fridge door open (b) run fans in empty rooms (c) use old filament bulbs (d) close the fridge quickly
14. 14.🧾 A 1000 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
15. 15.🧩 Which component senses how bright it is? (a) potentiometer (b) LDR (c) transistor (d) thermistor
16. 16.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
17. 17.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = R ÷ I (c) V = I ÷ R (d) V = I + R
18. 18.🔺 A current of 3 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🌈 In the resistor colour code, which number does brown stand for?
20. 20.What does a thermistor do? (a) boosts a small signal (b) glows using little power (c) makes things spin (d) senses how hot it is
21. 21.📏 How many kilowatts (kW) is 1650 W? =
22. 22.⚡ A device works on 5 V and takes 0.5 A. What is its power (in watts)? =
23. 23.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
24. 24.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an LED lamp (d) an oil lamp
25. 25.🔺 A current of 25 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
26. 26.True or false: power is measured in volts (V). (a) True (b) False
27. 27.What does a resistor do? (a) smooths a wobbly supply (b) stores a little charge (c) limits the current (d) makes a beeping sound
28. 28.Which of these saves electricity? (a) leave fridge door open (b) use old filament bulbs (c) unplug idle chargers (d) leave the TV on standby
29. 29.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
30. 30.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
31. 31.⚡ A 36 W device works on 12 V. What current does it take (in amperes)? =
32. 32.🔺 A 15 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
33. 33.True or false: a motor makes a beeping sound. (a) False (b) True
34. 34.🌈 A resistor has the colour bands red, orange, brown. What is its value (in ohms)?
35. 35.💡 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
36. 36.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
37. 37.📏 Which unit measures voltage? (a) ohm (Ω) (b) volt (V) (c) ampere (A) (d) watt (W)
38. 38.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it does not light (c) it changes colour (d) it makes a sound
39. 39.🔺 A current of 0.1 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)

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