Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 972 · 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 happens if an LED is put in backwards? (a) it changes colour (b) it makes a sound (c) it does not light (d) it lights brighter
2. 2.🔺 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
3. 3.🔍 Which is the odd one out? (a) iron one shirt at a time (b) close the fridge quickly (c) leave the TV on standby (d) run fans in empty rooms
4. 4.🧩 Which component senses how hot it is? (a) thermistor (b) capacitor (c) resistor (d) transistor
5. 5.🧩 Which component makes things spin? (a) thermistor (b) motor (c) transistor (d) capacitor
6. 6.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = V + I (d) P = I ÷ V
7. 7.🔍 Which is the odd one out? (a) leave fridge door open (b) switch off empty rooms (c) iron one shirt at a time (d) run fans in empty rooms
8. 8.💡 An LED is joined to a 6 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) does not light (c) may burn out
9. 9.⚡ Power tells us … (a) the size of a cell (b) the length of a wire (c) the colour of light (d) energy used each second
10. 10.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the widest gap (d) the gold band
11. 11.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
12. 12.🔺 A current of 0.2 A flows when 0.4 V is joined across a resistor. What is its resistance (in ohms)?
13. 13.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) stay the same (d) smaller
14. 14.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
15. 15.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) stays the same (c) gets bigger (d) becomes zero
16. 16.🧾 A family uses 110 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
17. 17.🔺 A current of 20 mA flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
18. 18.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 1000 (c) 60 (d) 10
19. 19.🧮 Resistors of 20 Ω, 47 Ω, 50 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
20. 20.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
21. 21.💡 Does it save or waste electricity to set the AC to 24 °C? (a) saves electricity (b) wastes electricity
22. 22.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
23. 23.True or false: an LDR has coloured bands. (a) False (b) True
24. 24.🔺 A current of 2.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🌈 A gold fourth band on a resistor means the value may be off by … (a) 5 % (b) 50 % (c) 0 % (d) 25 %
26. 26.True or false: to set the AC to 24 °C saves electricity. (a) False (b) True
27. 27.🔺 In the V-I-R triangle, how do we find V? (a) V = I + R (b) V = I × R (c) V = R ÷ I (d) V = I ÷ R
28. 28.🔺 A current of 1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
29. 29.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
30. 30.🔺 A current of 50 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
31. 31.🌈 A resistor has the colour bands orange, black, orange. What is its value in kilo-ohms (kΩ)? =
32. 32.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 950 Ω resistor? (a) white-green-black (b) green-white-brown (c) white-green-brown (d) white-green-red
33. 33.🔺 A 30 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
34. 34.🧩 Which component limits the current? (a) LDR (b) transistor (c) motor (d) resistor
35. 35.🌈 In the resistor colour code, which number does green stand for?
36. 36.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
37. 37.What does a capacitor do? (a) limits the current (b) is a resistance knob (c) smooths a wobbly supply (d) has coloured bands
38. 38.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
39. 39.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to store charge (d) to change its colour
40. 40.🔺 A current of 40 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =

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