Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 472 · 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: the ammeter measures current. (a) True (b) False
2. 2.True or false: the ammeter is joined across a part. (a) True (b) False
3. 3.🔺 A current of 1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🔺 A current of 50 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🌈 In the resistor colour code, which number does orange stand for?
6. 6.🔺 A current of 20 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
7. 7.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) energy used each second (d) the size of a cell
8. 8.💡 What does LED stand for? (a) light energy dial (b) low energy device (c) large electric dial (d) light-emitting diode
9. 9.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
10. 10.🔺 A current of 20 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
11. 11.🌈 A resistor has the colour bands brown, violet, black. What is its value (in ohms)?
12. 12.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
13. 13.🔺 A current of 10 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
14. 14.🔺 A current of 50 mA flows when 25 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.💡 An LED is joined to a 6 V battery through a 470 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
16. 16.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to change its colour (c) to store charge (d) to limit the current
17. 17.💡 What happens if an LED is put in backwards? (a) it does not light (b) it makes a sound (c) it changes colour (d) it lights brighter
18. 18.🔺 A current of 20 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
19. 19.📏 Which unit measures energy used each second? (a) watt (W) (b) ohm (Ω) (c) volt (V) (d) ampere (A)
20. 20.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = V × R (c) I = R ÷ V (d) I = V ÷ R
21. 21.⚡ A device works on 24 V and takes 1 A. What is its power (in watts)? =
22. 22.What does an LDR do? (a) stores a little charge (b) makes a beeping sound (c) lets current go one way (d) senses how bright it is
23. 23.🧩 Which component lets current go one way? (a) potentiometer (b) fuse (c) LED (d) diode
24. 24.What does a buzzer do? (a) is a resistance knob (b) smooths a wobbly supply (c) beeps for an alarm (d) limits the current
25. 25.🌈 In the resistor colour code, which number does yellow stand for?
26. 26.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
27. 27.🌈 In the resistor colour code, which number does blue stand for?
28. 28.True or false: the flow of charge is measured in volts (V). (a) False (b) True
29. 29.🌈 A resistor has the colour bands white, black, orange. What is its value in kilo-ohms (kΩ)? =
30. 30.🧮 A 22 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)?
31. 31.🧩 Which component stores a little charge? (a) transistor (b) capacitor (c) LED (d) resistor
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.🧮 Three equal 150 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
34. 34.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) zero (d) stay the same
35. 35.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
36. 36.🧮 Two resistors in parallel give a total that is … (a) always zero (b) more than either one (c) less than either one (d) their sum
37. 37.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.True or false: voltage is measured in watts (W). (a) True (b) False
39. 39.⚡ A device works on 9 V and takes 3 A. What is its power (in watts)? =
40. 40.🔺 A current of 1.5 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =

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