Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 917 · 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.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) measure heat (d) store charge briefly
2. 2.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 5 V supply. What current flows (in mA)?
3. 3.⚡ A 2.4 W device works on 24 V. What current does it take (in amperes)? =
4. 4.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) any band (d) the gold band
5. 5.🔺 A 40 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
6. 6.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 0 % (c) 25 % (d) 50 %
7. 7.🔍 Which is the odd one out? (a) set the AC to 24 °C (b) leave the TV on standby (c) switch off empty rooms (d) use LED lamps
8. 8.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
9. 9.What does a potentiometer do? (a) is a resistance knob (b) beeps for an alarm (c) has coloured bands (d) smooths a wobbly supply
10. 10.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a buzzer (c) a diode (d) a capacitor
11. 11.Which of these is measured in volts (V)? (a) how much a part resists (b) the push of a cell (c) power (d) energy used each second
12. 12.🔺 A current of 0.25 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
13. 13.⚡ A 0.5 W device works on 5 V. What current does it take (in amperes)? =
14. 14.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
15. 15.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 94 Ω resistor? (a) yellow-white-black (b) white-yellow-black (c) brown-yellow-black (d) white-yellow-brown
16. 16.🔺 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
17. 17.🧮 Resistors of 100 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
18. 18.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
19. 19.⚡ A device works on 12 V and takes 3 A. What is its power (in watts)? =
20. 20.🔺 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
21. 21.🔺 A current of 3 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
23. 23.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
24. 24.📏 Which unit measures the flow of charge? (a) volt (V) (b) ampere (A) (c) watt (W) (d) ohm (Ω)
25. 25.🔺 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
26. 26.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the size of a cell (d) the length of a wire
27. 27.🔺 A current of 0.25 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
28. 28.⚡ A device works on 3 V and takes 2 A. What is its power (in watts)? =
29. 29.🔺 A 24 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
30. 30.What does a buzzer do? (a) blows if current is high (b) beeps for an alarm (c) is a resistance knob (d) senses how bright it is
31. 31.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
32. 32.🌈 A resistor has the colour bands brown, green, orange. What is its value (in ohms)?
33. 33.📏 How many milliamperes (mA) is 0.6 A?
34. 34.🧮 A 20 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
35. 35.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) becomes zero (c) gets smaller (d) gets bigger
36. 36.⚡ A device works on 3 V and takes 0.25 A. What is its power (in watts)? =
37. 37.🔺 A current of 1 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
38. 38.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
39. 39.🧩 Which component beeps for an alarm? (a) buzzer (b) LDR (c) capacitor (d) potentiometer
40. 40.True or false: a buzzer glows using little power. (a) True (b) False

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