Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 47 · 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 2.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🧮 Five equal 50 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) a fuse (c) an LED (d) a resistor
4. 4.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) stay the same (d) zero
5. 5.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) gets bigger (c) becomes zero (d) stays the same
6. 6.🌈 Which band is read first on a resistor? (a) the widest gap (b) the gold band (c) any band (d) the one nearest an end
7. 7.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
8. 8.⚡ A 6 W device works on 3 V. What current does it take (in amperes)? =
9. 9.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
10. 10.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 80000 Ω resistor? (a) grey-black-orange (b) grey-black-yellow (c) white-grey-orange (d) grey-black-red
11. 11.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 5 % (c) 25 % (d) 50 %
12. 12.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
13. 13.Which of these wastes electricity? (a) set the AC to 24 °C (b) use LED lamps (c) use old filament bulbs (d) unplug idle chargers
14. 14.What does a capacitor do? (a) smooths a wobbly supply (b) lets current go one way (c) makes things spin (d) beeps for an alarm
15. 15.💡 Does it save or waste electricity to close the fridge quickly? (a) wastes electricity (b) saves electricity
16. 16.🌈 A resistor has the colour bands blue, yellow, black. What is its value (in ohms)?
17. 17.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
18. 18.🧮 A 68 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
19. 19.🔍 Which is the odd one out? (a) use old filament bulbs (b) use LED lamps (c) leave the TV on standby (d) leave fridge door open
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 91 Ω resistor? (a) white-brown-black (b) brown-white-black (c) white-brown-brown (d) brown-brown-black
21. 21.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
22. 22.🔺 A current of 0.25 A flows when 0.75 V is joined across a resistor. What is its resistance (in ohms)?
23. 23.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
24. 24.🧮 Resistors of 470 Ω, 20 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
25. 25.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🔺 A current of 25 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
27. 27.📏 How many amperes (A) is 400 mA? =
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.🔺 A current of 3 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
30. 30.What does a motor do? (a) turns a fan or wheels (b) lets current go one way (c) limits the current (d) makes a beeping sound
31. 31.🔍 Which is the odd one out? (a) use old filament bulbs (b) use LED lamps (c) set the AC to 24 °C (d) unplug idle chargers
32. 32.True or false: to switch off empty rooms wastes electricity. (a) True (b) False
33. 33.What does a fuse do? (a) blows if current is high (b) smooths a wobbly supply (c) lets current go one way (d) has coloured bands
34. 34.🧮 Resistors of 100 Ω and 33 Ω are joined in series. What is the total resistance (in ohms)?
35. 35.🌈 A resistor has the colour bands violet, white, black. What is its value (in ohms)?
36. 36.Which of these wastes electricity? (a) use LED lamps (b) close the fridge quickly (c) set the AC to 24 °C (d) iron one shirt at a time
37. 37.⚡ A device works on 1.5 V and takes 0.2 A. What is its power (in watts)? =
38. 38.🔺 A 50 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
39. 39.🌈 A resistor has the colour bands yellow, red, red. What is its value (in ohms)?
40. 40.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to limit the current (d) to store charge

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