Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 537 · 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.⚡ 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
2. 2.🔺 A current of 0.1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
4. 4.🔺 A current of 20 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
5. 5.True or false: power is measured in volts (V). (a) True (b) False
6. 6.📏 Which unit measures power? (a) ampere (A) (b) volt (V) (c) ohm (Ω) (d) watt (W)
7. 7.True or false: to leave fridge door open wastes electricity. (a) True (b) False
8. 8.True or false: an LED limits the current. (a) False (b) True
9. 9.🧮 Two equal 40 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
10. 10.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I × R (c) V = I + R (d) V = I ÷ R
11. 11.🔺 A current of 3 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
12. 12.Which of these is measured in watts (W)? (a) the flow of charge (b) energy used each second (c) voltage (d) resistance
13. 13.🧩 A capacitor in a circuit can … (a) measure heat (b) spin a wheel (c) store charge briefly (d) make light
14. 14.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 9 V supply. What resistor (in ohms) is needed in series?
15. 15.🔺 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
16. 16.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
17. 17.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 5 V supply. What current flows (in mA)?
18. 18.🔺 A current of 10 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
19. 19.⚡ A 1 W device works on 5 V. What current does it take (in amperes)? =
20. 20.🔺 A current of 2.5 A flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =
22. 22.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
23. 23.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
24. 24.🌈 In the resistor colour code, which number does black stand for?
25. 25.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
26. 26.🌈 A resistor has the colour bands blue, violet, orange. What is its value (in ohms)?
27. 27.🔺 A 1.25 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
28. 28.True or false: resistance is measured in ohms (Ω). (a) True (b) False
29. 29.🔺 A current of 0.1 A flows when 0.3 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.Which of these saves electricity? (a) use old filament bulbs (b) run fans in empty rooms (c) close the fridge quickly (d) leave the TV on standby
31. 31.🧾 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?
32. 32.🌈 Which band is read first on a resistor? (a) any band (b) the one nearest an end (c) the gold band (d) the widest gap
33. 33.🧩 Which component limits the current? (a) buzzer (b) resistor (c) thermistor (d) fuse
34. 34.🔺 A current of 10 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
35. 35.🔺 A 2 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?
36. 36.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 260 Ω resistor? (a) red-blue-black (b) red-blue-red (c) red-blue-brown (d) blue-red-brown
37. 37.⚡ A 12 W device works on 24 V. What current does it take (in amperes)? =
38. 38.🔺 A 0.6 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
39. 39.⚡ A 36 W device works on 12 V. What current does it take (in amperes)? =
40. 40.🌈 A resistor has the colour bands orange, white, yellow. What is its value in kilo-ohms (kΩ)? =

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