Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 37 · 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.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 10 (c) 60 (d) 1000
2. 2.📏 How many kilowatts (kW) is 4450 W? =
3. 3.True or false: a fuse has coloured bands. (a) False (b) True
4. 4.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🔺 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
6. 6.🔺 A current of 1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
7. 7.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
8. 8.💡 An LED is joined to a 5 V battery through a 1000 Ω 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
9. 9.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the size of a cell (d) the colour of light
10. 10.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 4 V supply. What current flows (in mA)?
11. 11.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
12. 12.Which of these wastes electricity? (a) unplug idle chargers (b) set the AC to 24 °C (c) iron one shirt at a time (d) close the fridge quickly
13. 13.⚡ A 0.3 W device works on 3 V. What current does it take (in amperes)? =
14. 14.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the widest gap (c) the gold band (d) any band
15. 15.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a candle (c) an oil lamp (d) a filament bulb
16. 16.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) bigger (d) stay the same
17. 17.🧮 A 20 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
18. 18.What does a motor do? (a) stores a little charge (b) glows using little power (c) has coloured bands (d) makes things spin
19. 19.True or false: voltage is measured in amperes (A). (a) False (b) True
20. 20.True or false: the ammeter measures voltage. (a) True (b) False
21. 21.🔺 A current of 0.25 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
22. 22.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
23. 23.🌈 A resistor has the colour bands white, yellow, orange. What is its value in kilo-ohms (kΩ)? =
24. 24.🔺 A current of 10 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
25. 25.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
26. 26.True or false: to leave fridge door open saves electricity. (a) False (b) True
27. 27.What does an LED do? (a) glows using little power (b) smooths a wobbly supply (c) turns a fan or wheels (d) limits the current
28. 28.🔺 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
29. 29.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) more than either one (d) their sum
30. 30.⚡ A device works on 9 V and takes 3 A. What is its power (in watts)? =
31. 31.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
32. 32.🧩 Which component makes a beeping sound? (a) LED (b) motor (c) transistor (d) buzzer
33. 33.🌈 In the resistor colour code, which number does black stand for?
34. 34.🔺 An 8 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
35. 35.🧾 A family uses 200 units of electricity in a month and each unit costs ₹5. What is the bill (in ₹)?
36. 36.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 10 hours. How many watt-hours (Wh) are saved?
37. 37.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = I ÷ V (d) P = V ÷ I
38. 38.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
39. 39.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) gets bigger (d) stays the same
40. 40.🌈 A resistor has the colour bands brown, orange, brown. What is its value (in ohms)?

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