Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 443 · 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 red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?
2. 2.🔺 A current of 20 mA flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
3. 3.💡 An LED is joined to a 12 V battery with no 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
4. 4.⚡ A device works on 12 V and takes 1 A. What is its power (in watts)? =
5. 5.🧩 Which part changes electrical energy into movement? (a) a resistor (b) a fuse (c) an LED (d) a motor
6. 6.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
7. 7.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
8. 8.💡 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
9. 9.📏 How many amperes (A) is 1320 mA? =
10. 10.True or false: to use LED lamps wastes electricity. (a) False (b) True
11. 11.True or false: the push of a cell is measured in ohms (Ω). (a) True (b) False
12. 12.🌈 In the resistor colour code, which number does black stand for?
13. 13.🔺 A current of 1.5 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
14. 14.🔺 A current of 0.1 A flows when 0.4 V is joined across a resistor. What is its resistance (in ohms)?
15. 15.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) gets smaller (c) stays the same (d) becomes zero
16. 16.📏 Which unit measures the push of a cell? (a) ohm (Ω) (b) ampere (A) (c) volt (V) (d) watt (W)
17. 17.🔍 Which is the odd one out? (a) run fans in empty rooms (b) leave fridge door open (c) use daylight to read (d) leave the TV on standby
18. 18.True or false: the ammeter is joined across a part. (a) False (b) True
19. 19.🔺 A 12 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
20. 20.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
21. 21.📏 How many milliamperes (mA) is 1.2 A?
22. 22.🧩 Which part changes electrical energy into sound? (a) a diode (b) a resistor (c) a buzzer (d) a capacitor
23. 23.Which of these is measured in amperes (A)? (a) power (b) the flow of charge (c) resistance (d) how much a part resists
24. 24.🔺 A current of 10 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🧩 A capacitor in a circuit can … (a) measure heat (b) spin a wheel (c) make light (d) store charge briefly
26. 26.🌈 A resistor has the colour bands grey, white, orange. What is its value in kilo-ohms (kΩ)? =
27. 27.🧮 A 20 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
28. 28.Which of these is measured in ohms (Ω)? (a) voltage (b) energy used each second (c) resistance (d) the push of a cell
29. 29.🧮 A 4.5 V battery is joined to 10 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
30. 30.🔺 A 0.4 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
31. 31.💡 What does LED stand for? (a) light-emitting diode (b) low energy device (c) large electric dial (d) light energy dial
32. 32.🔺 A current of 2 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
33. 33.⚡ A device works on 3 V and takes 0.2 A. What is its power (in watts)? =
34. 34.🌈 A resistor has the colour bands orange, yellow, brown. What is its value (in ohms)?
35. 35.True or false: a buzzer turns a fan or wheels. (a) True (b) False
36. 36.📏 How many milliamperes (mA) make 1 ampere? (a) 1000 (b) 60 (c) 100 (d) 10
37. 37.📏 Which unit measures voltage? (a) ampere (A) (b) ohm (Ω) (c) volt (V) (d) watt (W)
38. 38.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) more than either one (d) less than either one
39. 39.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

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