Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 849 · 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.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
2. 2.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.📏 Which unit measures the push of a cell? (a) ohm (Ω) (b) watt (W) (c) ampere (A) (d) volt (V)
4. 4.💡 An LED is joined to a 12 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) lights up (c) does not light
5. 5.🌈 In the resistor colour code, which number does grey stand for?
6. 6.⚡ A device works on 3 V and takes 0.5 A. What is its power (in watts)? =
7. 7.🔺 A current of 2.5 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
8. 8.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 45000 Ω resistor? (a) green-yellow-orange (b) yellow-green-red (c) yellow-green-orange (d) yellow-green-yellow
9. 9.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
10. 10.🧮 Two resistors in parallel give a total that is … (a) their sum (b) more than either one (c) less than either one (d) always zero
11. 11.⚡ A 3 W device works on 12 V. What current does it take (in amperes)? =
12. 12.🔺 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
13. 13.🌈 A resistor has the colour bands green, blue, black. What is its value (in ohms)?
14. 14.True or false: the push of a cell is measured in volts (V). (a) False (b) True
15. 15.What does a capacitor do? (a) boosts a small signal (b) blows if current is high (c) makes a beeping sound (d) smooths a wobbly supply
16. 16.🌈 A resistor has the colour bands violet, red, black. What is its value (in ohms)?
17. 17.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 4 hours. How many watt-hours (Wh) are saved?
18. 18.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
19. 19.📏 How many milliamperes (mA) is 1.48 A?
20. 20.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
21. 21.⚡ A 6 W device works on 3 V. What current does it take (in amperes)? =
22. 22.🧩 Which part changes electrical energy into movement? (a) a resistor (b) a fuse (c) an LED (d) a motor
23. 23.🔺 In the V-I-R triangle, how do we find I? (a) I = V × R (b) I = V + R (c) I = R ÷ V (d) I = V ÷ R
24. 24.🧮 A 33 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
25. 25.🔺 A 0.4 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
26. 26.What does a diode do? (a) blows if current is high (b) senses how hot it is (c) lets current go one way (d) makes a beeping sound
27. 27.🔺 A current of 1 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
28. 28.⚡ A 4.5 W device works on 9 V. What current does it take (in amperes)? =
29. 29.🔺 A current of 40 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.💡 Why does an LED need a resistor in series? (a) to store charge (b) to make it brighter (c) to change its colour (d) to limit the current
31. 31.🌈 A resistor has the colour bands green, red, red. What is its value (in ohms)?
32. 32.⚡ A 4.5 W device works on 3 V. What current does it take (in amperes)? =
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) does not light (b) may burn out (c) lights up
34. 34.💡 An LED is joined to a 9 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) lights up (c) does not light
35. 35.🧩 Which component senses how bright it is? (a) LDR (b) motor (c) fuse (d) resistor
36. 36.🔺 A current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
37. 37.📏 Which unit measures the flow of charge? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
38. 38.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
39. 39.⚡ A device works on 1.5 V and takes 1 A. What is its power (in watts)? =
40. 40.⚡ A device works on 12 V and takes 2 A. What is its power (in watts)? =

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