Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 484 · 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.⚡ Which formula gives electric power? (a) P = V + I (b) P = V × I (c) P = V ÷ I (d) P = I ÷ V
2. 2.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) stays the same (b) gets bigger (c) becomes zero (d) gets smaller
3. 3.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
4. 4.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) the gold band (c) the widest gap (d) any band
5. 5.🔺 A current of 0.25 A flows when 1 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
7. 7.⚡ A device works on 5 V and takes 1 A. What is its power (in watts)? =
8. 8.📏 Which unit measures power? (a) volt (V) (b) ampere (A) (c) ohm (Ω) (d) watt (W)
9. 9.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = I ÷ V (c) R = V + I (d) R = V × I
10. 10.📏 Which unit measures how much a part resists? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
11. 11.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
12. 12.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a diode (c) a resistor (d) a buzzer
13. 13.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
14. 14.⚡ A device works on 12 V and takes 0.5 A. What is its power (in watts)? =
15. 15.⚡ A 6 W device works on 24 V. What current does it take (in amperes)? =
16. 16.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) stay the same (c) zero (d) bigger
17. 17.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 2100 Ω resistor? (a) red-brown-brown (b) red-brown-orange (c) brown-red-red (d) red-brown-red
18. 18.🧾 A 250 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
19. 19.🧮 A 33 Ω resistor is joined in series with two equal 50 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
20. 20.📏 Which unit measures the push of a cell? (a) ampere (A) (b) watt (W) (c) ohm (Ω) (d) volt (V)
21. 21.True or false: the ammeter measures current. (a) True (b) False
22. 22.🔺 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
23. 23.🔺 A 0.6 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
24. 24.🧮 A 3.5 V battery is joined to 10 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
25. 25.🌈 A resistor has the colour bands yellow, red, red. What is its value in kilo-ohms (kΩ)? =
26. 26.⚡ A 4.5 W device works on 3 V. What current does it take (in amperes)? =
27. 27.💡 An LED is joined to a 3 V battery through a 330 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) lights up (b) may burn out (c) does not light
28. 28.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
29. 29.🔺 A current of 0.1 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
30. 30.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = R ÷ V (c) I = V + R (d) I = V × R
31. 31.🧾 A 500 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
32. 32.🔺 A current of 20 mA flows when 2.4 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.Which of these wastes electricity? (a) use LED lamps (b) set the AC to 24 °C (c) leave the TV on standby (d) unplug idle chargers
34. 34.True or false: to use daylight to read saves electricity. (a) True (b) False
35. 35.⚡ A device works on 6 V and takes 0.5 A. What is its power (in watts)? =
36. 36.🌈 A resistor has the colour bands violet, orange, red. What is its value (in ohms)?
37. 37.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to change its colour (c) to make it brighter (d) to store charge
38. 38.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.🔺 An 8 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
40. 40.💡 An LED is joined to a 3 V battery through a 1000 Ω resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) may burn out (b) does not light (c) lights up

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