Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 463 · 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.🌈 In the resistor colour code, which number does blue stand for?
2. 2.⚡ A 4.5 W device works on 3 V. What current does it take (in amperes)? =
3. 3.True or false: the voltmeter is joined in series. (a) False (b) True
4. 4.🔺 A current of 0.1 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
5. 5.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
6. 6.True or false: a resistor stores a little charge. (a) True (b) False
7. 7.🧮 A 47 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)?
8. 8.🌈 Which band is read first on a resistor? (a) the widest gap (b) the gold band (c) the one nearest an end (d) any band
9. 9.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
10. 10.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 2.5 V supply. What current flows (in mA)?
11. 11.🔍 Which is the odd one out? (a) run fans in empty rooms (b) unplug idle chargers (c) leave fridge door open (d) iron one shirt at a time
12. 12.🔺 A 0.4 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
13. 13.🧮 Resistors of 100 Ω, 20 Ω, 330 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
14. 14.📏 How many watts (W) is 0.2 kW?
15. 15.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) stays the same (c) gets bigger (d) gets smaller
16. 16.🌈 A resistor has the colour bands grey, yellow, orange. What is its value in kilo-ohms (kΩ)? =
17. 17.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
18. 18.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to limit the current (c) to store charge (d) to make it brighter
19. 19.What does a potentiometer do? (a) has coloured bands (b) senses how hot it is (c) is a resistance knob (d) blows if current is high
20. 20.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 9 hours. How many watt-hours (Wh) are saved?
21. 21.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = I ÷ V (d) R = V + I
22. 22.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) the flow of water (c) the pipe colour (d) a narrow pipe
23. 23.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
24. 24.True or false: to close the fridge quickly wastes electricity. (a) True (b) False
25. 25.🧮 A 47 Ω resistor is joined in series with two equal 20 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
26. 26.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.True or false: a capacitor beeps for an alarm. (a) False (b) True
28. 28.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) less than either one (c) always zero (d) their sum
29. 29.True or false: to switch off empty rooms saves electricity. (a) False (b) True
30. 30.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
31. 31.🌈 A resistor has the colour bands blue, black, yellow. What is its value in kilo-ohms (kΩ)? =
32. 32.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = I + R (c) V = I × R (d) V = R ÷ I
33. 33.🔺 A current of 3 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
34. 34.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
35. 35.🔺 A current of 2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
36. 36.🧾 A 50 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
37. 37.💡 What does LED stand for? (a) light-emitting diode (b) large electric dial (c) light energy dial (d) low energy device
38. 38.True or false: to use LED lamps wastes electricity. (a) True (b) False
39. 39.🔺 A current of 40 mA flows through a 500 Ω resistor. What is the voltage across it (in volts)? =
40. 40.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)

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