Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 343 · 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) energy used each second (d) the length of a wire
2. 2.💡 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)?
3. 3.True or false: a diode smooths a wobbly supply. (a) True (b) False
4. 4.📏 How many kilowatts (kW) is 4150 W? =
5. 5.True or false: a capacitor smooths a wobbly supply. (a) True (b) False
6. 6.🧮 Resistors of 10 Ω, 100 Ω and 220 Ω are joined in series. What is the total resistance (in ohms)?
7. 7.🧮 Two resistors in parallel give a total that is … (a) always zero (b) more than either one (c) their sum (d) less than either one
8. 8.⚡ A 15 W device works on 5 V. What current does it take (in amperes)? =
9. 9.💡 A red LED uses 2 V and should get 25 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
10. 10.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
11. 11.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 40000 Ω resistor? (a) green-yellow-orange (b) yellow-black-orange (c) yellow-black-red (d) yellow-black-yellow
12. 12.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it changes colour (d) it does not light
13. 13.⚡ A 1.2 W device works on 6 V. What current does it take (in amperes)? =
14. 14.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
15. 15.Which of these is measured in volts (V)? (a) resistance (b) current (c) the push of a cell (d) power
16. 16.📏 How many amperes (A) is 2120 mA? =
17. 17.💡 An LED is joined to a 3 V battery through a 1000 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) does not light (c) lights up
18. 18.🔺 A 1.6 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
19. 19.🔺 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
20. 20.🌈 A resistor has the colour bands white, green, brown. What is its value (in ohms)?
21. 21.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
22. 22.True or false: a motor beeps for an alarm. (a) False (b) True
23. 23.⚡ A 24 W device works on 12 V. What current does it take (in amperes)? =
24. 24.🌈 A resistor has the colour bands brown, grey, yellow. What is its value in kilo-ohms (kΩ)? =
25. 25.🔺 A current of 25 mA flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
26. 26.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
27. 27.True or false: to switch off empty rooms wastes electricity. (a) False (b) True
28. 28.True or false: to use LED lamps wastes electricity. (a) True (b) False
29. 29.🔺 A current of 0.5 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
30. 30.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
31. 31.🧮 Resistors of 33 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
32. 32.🔺 A 10 V supply is joined across a 400 Ω resistor. What current flows (in milliamperes, mA)?
33. 33.🧩 A capacitor in a circuit can … (a) measure heat (b) store charge briefly (c) make light (d) spin a wheel
34. 34.Which of these is measured in volts (V)? (a) resistance (b) power (c) voltage (d) energy used each second
35. 35.🧾 A 1500 W appliance runs for 10 hours. How many units (kWh) of electricity does it use? =
36. 36.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
37. 37.📏 How many ohms (Ω) is 0.2 kΩ?
38. 38.🌈 In the resistor colour code, which number does brown stand for?
39. 39.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
40. 40.🧾 A 200 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =

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