Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 117 · 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 resistor has the colour bands green, green, orange. What is its value (in ohms)?
2. 2.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 57000 Ω resistor? (a) green-violet-orange (b) green-violet-yellow (c) green-violet-red (d) violet-green-orange
3. 3.⚡ A device works on 3 V and takes 0.25 A. What is its power (in watts)? =
4. 4.🌈 In the resistor colour code, which number does grey stand for?
5. 5.🔺 A 10 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
6. 6.True or false: resistance is measured in watts (W). (a) True (b) False
7. 7.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
8. 8.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
9. 9.Which of these is measured in watts (W)? (a) resistance (b) current (c) power (d) how much a part resists
10. 10.🌈 A resistor has the colour bands red, green, red. What is its value in kilo-ohms (kΩ)? =
11. 11.🔺 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
12. 12.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
13. 13.True or false: the push of a cell is measured in ohms (Ω). (a) False (b) True
14. 14.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
15. 15.💡 Does it save or waste electricity to run fans in empty rooms? (a) wastes electricity (b) saves electricity
16. 16.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 3.5 V supply. What current flows (in mA)?
17. 17.⚡ Power tells us … (a) the colour of light (b) the size of a cell (c) the length of a wire (d) energy used each second
18. 18.Which of these wastes electricity? (a) set the AC to 24 °C (b) leave fridge door open (c) switch off empty rooms (d) unplug idle chargers
19. 19.📏 How many watts (W) is 3 kW?
20. 20.True or false: to switch off empty rooms wastes electricity. (a) False (b) True
21. 21.🔺 A 6 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
22. 22.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 1000 (c) 60 (d) 10
23. 23.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) bigger (d) smaller
24. 24.True or false: the ammeter is joined across a part. (a) True (b) False
25. 25.🔺 A current of 0.1 A flows when 0.8 V is joined across a resistor. What is its resistance (in ohms)?
26. 26.💡 Does it save or waste electricity to leave fridge door open? (a) wastes electricity (b) saves electricity
27. 27.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 130 Ω resistor? (a) brown-orange-red (b) brown-orange-brown (c) orange-brown-brown (d) brown-orange-black
28. 28.🔺 A current of 20 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
29. 29.🔍 Which is the odd one out? (a) iron one shirt at a time (b) leave the TV on standby (c) use old filament bulbs (d) close the fridge quickly
30. 30.🌈 In the resistor colour code, which number does red stand for?
31. 31.🔺 A current of 2.5 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
32. 32.🔺 A 20 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
33. 33.⚡ A 2.5 W device works on 5 V. What current does it take (in amperes)? =
34. 34.True or false: the voltmeter measures voltage. (a) False (b) True
35. 35.🌈 A resistor has the colour bands grey, yellow, yellow. What is its value in kilo-ohms (kΩ)? =
36. 36.🔺 A 1.2 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
37. 37.What does a resistor do? (a) makes a beeping sound (b) has coloured bands (c) makes things spin (d) lets current go one way
38. 38.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) measure heat (d) spin a wheel
39. 39.🧮 Resistors of 33 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
40. 40.🔺 A current of 20 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =

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