Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 801 · 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 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?
2. 2.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
3. 3.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) smaller (d) stay the same
4. 4.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 72000 Ω resistor? (a) red-violet-orange (b) violet-red-yellow (c) violet-red-red (d) violet-red-orange
5. 5.⚡ A 2.5 W device works on 5 V. What current does it take (in amperes)? =
6. 6.⚡ A 24 W device works on 24 V. What current does it take (in amperes)? =
7. 7.🧮 A 4 V battery is joined to 10 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
8. 8.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
9. 9.📏 Which unit measures voltage? (a) ampere (A) (b) watt (W) (c) ohm (Ω) (d) volt (V)
10. 10.🌈 A resistor has the colour bands red, grey, black. What is its value (in ohms)?
11. 11.True or false: the flow of charge is measured in volts (V). (a) True (b) False
12. 12.True or false: the ammeter is joined in series. (a) False (b) True
13. 13.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a resistor (c) a diode (d) a capacitor
14. 14.💡 An LED is joined to a 6 V battery through a 220 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) lights up (b) does not light (c) may burn out
15. 15.True or false: a potentiometer boosts a small signal. (a) True (b) False
16. 16.🧮 Two resistors in parallel give a total that is … (a) always zero (b) less than either one (c) their sum (d) more than either one
17. 17.🔺 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
18. 18.⚡ A device works on 5 V and takes 0.25 A. What is its power (in watts)? =
19. 19.True or false: a potentiometer blows if current is high. (a) False (b) True
20. 20.True or false: current is measured in ohms (Ω). (a) True (b) False
21. 21.🔺 A current of 0.2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
22. 22.🔺 A current of 3 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🌈 A resistor has the colour bands white, grey, yellow. What is its value in kilo-ohms (kΩ)? =
24. 24.🔺 A current of 40 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
25. 25.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1024 (b) 10 (c) 100 (d) 1000
26. 26.📏 Voltmeter or ammeter: which one measures current? (a) ammeter (b) voltmeter
27. 27.🌈 A resistor has the colour bands red, red, orange. What is its value (in ohms)?
28. 28.💡 What does LED stand for? (a) light-emitting diode (b) light energy dial (c) low energy device (d) large electric dial
29. 29.🔺 A current of 50 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.Which of these is measured in volts (V)? (a) how much a part resists (b) the flow of charge (c) resistance (d) voltage
31. 31.🌈 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
32. 32.🔺 A current of 0.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
33. 33.What does a diode do? (a) blows if current is high (b) lets current go one way (c) makes things spin (d) glows using little power
34. 34.🌈 A resistor has the colour bands white, black, orange. What is its value in kilo-ohms (kΩ)? =
35. 35.🧾 One “unit” on an electricity bill is … (a) 1 ampere (b) 1 watt (c) 1 volt (d) 1 kilowatt-hour (kWh)
36. 36.True or false: to use old filament bulbs wastes electricity. (a) True (b) False
37. 37.🔺 A current of 20 mA flows when 10 V is joined across a resistor. What is its resistance (in ohms)?
38. 38.🔺 A 12.5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
39. 39.🔺 A current of 2.5 A flows when 12.5 V is joined across a resistor. What is its resistance (in ohms)?
40. 40.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

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