Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 651 · 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 does an LDR do? (a) makes a beeping sound (b) senses how bright it is (c) glows using little power (d) beeps for an alarm
2. 2.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) bigger (d) smaller
4. 4.🔍 Which is the odd one out? (a) switch off empty rooms (b) leave fridge door open (c) run fans in empty rooms (d) leave the TV on standby
5. 5.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
6. 6.True or false: on an LED, the round-side leg is the anode (+). (a) False (b) True
7. 7.🔺 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
8. 8.🔺 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
9. 9.What does a resistor do? (a) senses how bright it is (b) has coloured bands (c) boosts a small signal (d) lets current go one way
10. 10.🔍 Which is the odd one out? (a) switch off empty rooms (b) use daylight to read (c) close the fridge quickly (d) iron one shirt at a time
11. 11.⚡ A 0.3 W device works on 1.5 V. What current does it take (in amperes)? =
12. 12.⚡ Power tells us … (a) the length of a wire (b) the size of a cell (c) energy used each second (d) the colour of light
13. 13.Which of these is measured in volts (V)? (a) energy used each second (b) power (c) voltage (d) current
14. 14.True or false: to use old filament bulbs wastes electricity. (a) True (b) False
15. 15.⚡ A 0.3 W device works on 3 V. What current does it take (in amperes)? =
16. 16.📏 Which unit measures voltage? (a) ohm (Ω) (b) watt (W) (c) ampere (A) (d) volt (V)
17. 17.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
18. 18.🧩 Which component blows if current is high? (a) transistor (b) resistor (c) capacitor (d) fuse
19. 19.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
20. 20.🧩 Which component glows using little power? (a) resistor (b) capacitor (c) diode (d) LED
21. 21.Which of these wastes electricity? (a) leave fridge door open (b) set the AC to 24 °C (c) switch off empty rooms (d) use daylight to read
22. 22.What does an LED do? (a) has coloured bands (b) glows using little power (c) limits the current (d) lets current go one way
23. 23.📏 Which unit measures how much a part resists? (a) watt (W) (b) ampere (A) (c) ohm (Ω) (d) volt (V)
24. 24.True or false: to close the fridge quickly saves electricity. (a) False (b) True
25. 25.True or false: a transistor is a resistance knob. (a) False (b) True
26. 26.🌈 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
27. 27.🧮 A 330 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
28. 28.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) becomes zero (c) stays the same (d) gets bigger
29. 29.What does a motor do? (a) stores a little charge (b) limits the current (c) lets current go one way (d) makes things spin
30. 30.📏 How many milliamperes (mA) is 0.75 A?
31. 31.🔺 A 2.4 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
32. 32.🧾 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
33. 33.📏 How many kilowatts (kW) is 3850 W? =
34. 34.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 0 % (d) 25 %
35. 35.🔺 A current of 0.25 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
36. 36.Which of these saves electricity? (a) switch off empty rooms (b) use old filament bulbs (c) run fans in empty rooms (d) leave the TV on standby
37. 37.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
38. 38.What does a buzzer do? (a) beeps for an alarm (b) smooths a wobbly supply (c) is a resistance knob (d) blows if current is high
39. 39.True or false: how much a part resists is measured in ohms (Ω). (a) False (b) True
40. 40.What does a resistor do? (a) smooths a wobbly supply (b) senses how hot it is (c) beeps for an alarm (d) limits the current

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