Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 356 · 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 current of 10 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.⚡ 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
4. 4.⚡ A device works on 12 V and takes 2 A. What is its power (in watts)? =
5. 5.🔺 A current of 1 A flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.🔺 A current of 50 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
7. 7.💡 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?
8. 8.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
9. 9.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
10. 10.True or false: the ammeter measures current. (a) False (b) True
11. 11.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 790 Ω resistor? (a) violet-white-brown (b) violet-white-red (c) violet-white-black (d) white-violet-brown
12. 12.🧾 A 1000 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
13. 13.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
14. 14.🧮 A 33 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
15. 15.🔺 An 11.75 V supply is joined across a 470 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.True or false: an LDR makes things spin. (a) True (b) False
17. 17.⚡ A device works on 1.5 V and takes 2 A. What is its power (in watts)? =
18. 18.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
19. 19.🧩 Which component senses how bright it is? (a) resistor (b) LDR (c) motor (d) LED
20. 20.🔺 A current of 0.25 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a filament bulb (c) a candle (d) an oil lamp
22. 22.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
23. 23.🔺 A 7.5 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
24. 24.📏 Voltmeter or ammeter: which one is joined across a part? (a) voltmeter (b) ammeter
25. 25.🧮 A 1 V battery is joined to 2 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
26. 26.⚡ A 12 W device works on 6 V. What current does it take (in amperes)? =
27. 27.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
28. 28.🔺 A 0.8 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
29. 29.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 2.75 V supply. What current flows (in mA)?
30. 30.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
31. 31.⚡ A device works on 6 V and takes 2 A. What is its power (in watts)? =
32. 32.🔺 A current of 2.5 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🌈 In the resistor colour code, which number does yellow stand for?
34. 34.🧾 A 200 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
35. 35.🧮 Resistors of 47 Ω, 22 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
36. 36.💡 What does LED stand for? (a) large electric dial (b) low energy device (c) light energy dial (d) light-emitting diode
37. 37.🔺 A current of 2.5 A flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
38. 38.Which of these saves electricity? (a) run fans in empty rooms (b) unplug idle chargers (c) use old filament bulbs (d) iron one shirt at a time
39. 39.🌈 A resistor has the colour bands green, brown, yellow. What is its value in kilo-ohms (kΩ)? =
40. 40.📏 Which unit measures energy used each second? (a) watt (W) (b) ohm (Ω) (c) ampere (A) (d) volt (V)

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