Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 669 · 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 45 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
2. 2.Which of these wastes electricity? (a) leave fridge door open (b) switch off empty rooms (c) close the fridge quickly (d) set the AC to 24 °C
3. 3.🔺 A 1.2 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
4. 4.⚡ A device works on 9 V and takes 3 A. What is its power (in watts)? =
5. 5.⚡ Which formula gives electric power? (a) P = V ÷ I (b) P = V + I (c) P = I ÷ V (d) P = V × I
6. 6.🔺 A current of 50 mA flows through a 200 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🌈 A resistor has the colour bands blue, black, orange. What is its value (in ohms)?
8. 8.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
9. 9.True or false: to use LED lamps wastes electricity. (a) False (b) True
10. 10.🔺 A 15 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
11. 11.True or false: a resistor smooths a wobbly supply. (a) False (b) True
12. 12.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
13. 13.💡 Does it save or waste electricity to use daylight to read? (a) wastes electricity (b) saves electricity
14. 14.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
15. 15.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
16. 16.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) zero (d) stay the same
17. 17.🧮 A 20 Ω resistor is joined in series with two equal 470 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
18. 18.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the colour of light (d) the length of a wire
19. 19.📏 Which unit measures voltage? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
20. 20.📏 How many watts (W) is 3.7 kW?
21. 21.True or false: resistance is measured in volts (V). (a) False (b) True
22. 22.🌈 Which band is read first on a resistor? (a) the gold band (b) the one nearest an end (c) the widest gap (d) any band
23. 23.🧩 Which component has coloured bands? (a) fuse (b) diode (c) buzzer (d) resistor
24. 24.🧮 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
25. 25.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
26. 26.⚡ A device works on 9 V and takes 0.2 A. What is its power (in watts)? =
27. 27.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
28. 28.💡 What does LED stand for? (a) light energy dial (b) light-emitting diode (c) low energy device (d) large electric dial
29. 29.📏 How many milliamperes (mA) make 1 ampere? (a) 100 (b) 60 (c) 1000 (d) 10
30. 30.True or false: a buzzer turns a fan or wheels. (a) True (b) False
31. 31.🔺 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
32. 32.🔺 A current of 40 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🧩 Which component glows using little power? (a) LED (b) motor (c) resistor (d) diode
34. 34.True or false: the ammeter measures current. (a) True (b) False
35. 35.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) spin a wheel (d) measure heat
36. 36.🧮 A 10 Ω resistor is joined in series with two equal 330 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
37. 37.🔺 A 2.5 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
38. 38.🧮 Resistors of 470 Ω, 220 Ω, 47 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
39. 39.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 110 Ω resistor? (a) brown-brown-red (b) brown-brown-brown (c) brown-brown-black (d) brown-red-brown
40. 40.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 6.5 V supply. What current flows (in mA)?

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