Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 439 · 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.True or false: on an LED, the shorter leg is the cathode (−). (a) True (b) False
2. 2.🔺 A current of 50 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🧮 Resistors of 330 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
4. 4.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to store charge (c) to change its colour (d) to limit the current
5. 5.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = R ÷ I (d) V = I × R
6. 6.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.🔺 A current of 50 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
8. 8.🌈 A resistor has the colour bands violet, orange, yellow. What is its value in kilo-ohms (kΩ)? =
9. 9.🧮 An 8 V battery is joined to 12 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
10. 10.🔺 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
11. 11.🧮 Resistors of 33 Ω, 47 Ω, 68 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
12. 12.📏 Which unit measures voltage? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
13. 13.🔺 A 0.8 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
14. 14.🔺 A current of 0.5 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
16. 16.🔺 A 2.5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
17. 17.Which of these saves electricity? (a) use old filament bulbs (b) leave the TV on standby (c) run fans in empty rooms (d) switch off empty rooms
18. 18.🌈 In the resistor colour code, which number does yellow stand for?
19. 19.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 100 (b) 1024 (c) 1000 (d) 10
20. 20.💡 Does it save or waste electricity to use old filament bulbs? (a) wastes electricity (b) saves electricity
21. 21.🧮 A 10 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
22. 22.🌈 Which band is read first on a resistor? (a) any band (b) the gold band (c) the widest gap (d) the one nearest an end
23. 23.🧩 Which component beeps for an alarm? (a) thermistor (b) buzzer (c) LDR (d) LED
24. 24.📏 How many kilowatts (kW) is 350 W? =
25. 25.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) stay the same (d) zero
26. 26.🔺 A 2.4 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
27. 27.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
28. 28.📏 Which unit measures the flow of charge? (a) watt (W) (b) ohm (Ω) (c) ampere (A) (d) volt (V)
29. 29.🔺 A 16 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
30. 30.💡 An LED is joined to a 5 V battery through a 330 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
31. 31.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
32. 32.🔺 A current of 10 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
33. 33.True or false: a resistor has coloured bands. (a) False (b) True
34. 34.🧮 Resistors of 50 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
35. 35.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
36. 36.🔺 A current of 3 A flows when 36 V is joined across a resistor. What is its resistance (in ohms)?
37. 37.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = V + I (d) P = I ÷ V
38. 38.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 770 Ω resistor? (a) violet-violet-red (b) violet-violet-black (c) violet-violet-brown (d) violet-grey-brown
39. 39.🔺 A current of 40 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🧮 Two equal 10 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

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