Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 452 · 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 red LED uses 2 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
2. 2.🔺 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
3. 3.🧩 Which component senses how hot it is? (a) capacitor (b) potentiometer (c) LED (d) thermistor
4. 4.🔺 A current of 10 mA flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
6. 6.🧾 A family uses 30 units of electricity in a month and each unit costs ₹6. What is the bill (in ₹)?
7. 7.🔺 A 4 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
8. 8.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) the one nearest an end (d) any band
9. 9.💡 What does LED stand for? (a) low energy device (b) light-emitting diode (c) large electric dial (d) light energy dial
10. 10.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V × I (c) P = I ÷ V (d) P = V + I
11. 11.⚡ An 18 W device works on 6 V. What current does it take (in amperes)? =
12. 12.Which of these is measured in ohms (Ω)? (a) current (b) how much a part resists (c) energy used each second (d) power
13. 13.🔺 A current of 25 mA flows when 6.25 V is joined across a resistor. What is its resistance (in ohms)?
14. 14.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) the length of a wire (d) energy used each second
15. 15.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it changes colour (c) it lights brighter (d) it does not light
16. 16.💡 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) does not light (c) lights up
17. 17.💡 An LED is joined to a 9 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
18. 18.🔺 A current of 50 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🔺 A 6.25 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?
20. 20.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
21. 21.Which of these is measured in volts (V)? (a) how much a part resists (b) voltage (c) the flow of charge (d) energy used each second
22. 22.⚡ A device works on 12 V and takes 0.25 A. What is its power (in watts)? =
23. 23.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
24. 24.Which of these is measured in watts (W)? (a) current (b) the flow of charge (c) the push of a cell (d) energy used each second
25. 25.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
26. 26.True or false: resistance is measured in ohms (Ω). (a) True (b) False
27. 27.🧾 A 100 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
28. 28.True or false: the voltmeter measures voltage. (a) False (b) True
29. 29.🔺 A current of 10 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.📏 How many kilo-ohms (kΩ) is 300 Ω? =
31. 31.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
32. 32.🌈 A resistor has the colour bands red, yellow, red. What is its value in kilo-ohms (kΩ)? =
33. 33.🔺 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
34. 34.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
35. 35.🔺 A current of 0.1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
36. 36.True or false: to run fans in empty rooms saves electricity. (a) True (b) False
37. 37.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
38. 38.What does an LDR do? (a) senses how bright it is (b) lets current go one way (c) limits the current (d) has coloured bands
39. 39.🔺 A current of 0.2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🔺 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

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