Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 788 · 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.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
2. 2.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
3. 3.🧩 Which part changes electrical energy into movement? (a) a motor (b) an LED (c) a fuse (d) a resistor
4. 4.🧩 Which component glows using little power? (a) motor (b) LED (c) thermistor (d) LDR
5. 5.True or false: the voltmeter is joined across a part. (a) False (b) True
6. 6.🔍 Which is the odd one out? (a) close the fridge quickly (b) unplug idle chargers (c) leave fridge door open (d) switch off empty rooms
7. 7.🔺 A current of 20 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
8. 8.True or false: energy used each second is measured in volts (V). (a) True (b) False
9. 9.What does a capacitor do? (a) glows using little power (b) smooths a wobbly supply (c) makes a beeping sound (d) senses how hot it is
10. 10.🌈 A resistor has the colour bands grey, yellow, yellow. What is its value in kilo-ohms (kΩ)? =
11. 11.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
12. 12.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = V × I (c) R = I ÷ V (d) R = V + I
13. 13.🌈 In the resistor colour code, which number does red stand for?
14. 14.🧮 Resistors of 47 Ω, 10 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
15. 15.True or false: the ammeter is joined across a part. (a) True (b) False
16. 16.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
17. 17.🧮 Resistors of 68 Ω and 22 Ω are joined in series. What is the total resistance (in ohms)?
18. 18.📏 How many milliamperes (mA) is 2.49 A?
19. 19.🔺 A 5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 33000 Ω resistor? (a) orange-yellow-orange (b) orange-orange-yellow (c) orange-orange-orange (d) orange-orange-red
21. 21.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
22. 22.What does a thermistor do? (a) glows using little power (b) stores a little charge (c) boosts a small signal (d) senses how hot it is
23. 23.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets bigger (c) gets smaller (d) stays the same
24. 24.🔍 Which is the odd one out? (a) leave the TV on standby (b) switch off empty rooms (c) use LED lamps (d) use daylight to read
25. 25.🧮 A 22 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
26. 26.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
27. 27.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
28. 28.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
29. 29.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
30. 30.What does an LDR do? (a) lets current go one way (b) blows if current is high (c) turns a fan or wheels (d) senses how bright it is
31. 31.True or false: a thermistor boosts a small signal. (a) False (b) True
32. 32.🧾 A family uses 100 units of electricity in a month and each unit costs ₹4. What is the bill (in ₹)?
33. 33.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 0 % (c) 5 % (d) 25 %
34. 34.💡 A blue LED uses 3 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
35. 35.⚡ A 27 W device works on 9 V. What current does it take (in amperes)? =
36. 36.True or false: to iron one shirt at a time saves electricity. (a) False (b) True
37. 37.📏 Which unit measures voltage? (a) volt (V) (b) ohm (Ω) (c) ampere (A) (d) watt (W)
38. 38.Which of these wastes electricity? (a) use daylight to read (b) switch off empty rooms (c) set the AC to 24 °C (d) iron one shirt at a time
39. 39.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
40. 40.🔺 A current of 0.25 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =

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