Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 812 · 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 measures voltage? (a) ammeter (b) voltmeter
2. 2.🧾 A 100 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
3. 3.📏 How many ohms (Ω) is 2.3 kΩ?
4. 4.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 25 % (d) 0 %
5. 5.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) bigger (d) smaller
6. 6.🔺 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
7. 7.🔺 A 12 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
8. 8.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the gold band (d) the widest gap
9. 9.💡 What happens if an LED is put in backwards? (a) it changes colour (b) it makes a sound (c) it lights brighter (d) it does not light
10. 10.🌈 A resistor has the colour bands red, brown, red. What is its value in kilo-ohms (kΩ)? =
11. 11.🧩 Which component makes a beeping sound? (a) resistor (b) potentiometer (c) capacitor (d) buzzer
12. 12.🔺 An 18 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
13. 13.True or false: a motor has coloured bands. (a) False (b) True
14. 14.🔺 A 7.5 V supply is joined across a 150 Ω resistor. What current flows (in milliamperes, mA)?
15. 15.⚡ A 0.75 W device works on 1.5 V. What current does it take (in amperes)? =
16. 16.True or false: a diode smooths a wobbly supply. (a) False (b) True
17. 17.🌈 In the resistor colour code, which number does yellow stand for?
18. 18.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?
19. 19.What does a transistor do? (a) senses how hot it is (b) stores a little charge (c) is a resistance knob (d) boosts a small signal
20. 20.🌈 A resistor has the colour bands yellow, white, orange. What is its value in kilo-ohms (kΩ)? =
21. 21.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
22. 22.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
23. 23.What does a motor do? (a) makes a beeping sound (b) boosts a small signal (c) limits the current (d) makes things spin
24. 24.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to store charge (c) to change its colour (d) to make it brighter
25. 25.🧮 A 20 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)?
26. 26.What does a thermistor do? (a) has coloured bands (b) glows using little power (c) limits the current (d) senses how hot it is
27. 27.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a diode (c) a capacitor (d) a resistor
28. 28.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
29. 29.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
30. 30.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
31. 31.🔺 A current of 0.2 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
33. 33.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = I ÷ V (c) P = V × I (d) P = V + I
34. 34.🧮 A 3.6 V battery is joined to 6 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
35. 35.🔺 A current of 50 mA flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.True or false: the voltmeter is joined in series. (a) True (b) False
37. 37.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an LED lamp (c) a candle (d) an oil lamp
38. 38.📏 Which unit measures power? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
39. 39.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
40. 40.Which of these is measured in ohms (Ω)? (a) resistance (b) the push of a cell (c) power (d) energy used each second

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