Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 574 · 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 current of 40 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
2. 2.🧮 Resistors of 68 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
3. 3.Which of these wastes electricity? (a) switch off empty rooms (b) unplug idle chargers (c) set the AC to 24 °C (d) leave the TV on standby
4. 4.🔺 A current of 50 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🧾 Which lamp gives the same light for the least power? (a) a candle (b) an oil lamp (c) a filament bulb (d) an LED lamp
6. 6.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
7. 7.🧮 Resistors of 50 Ω, 20 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
8. 8.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
9. 9.🔺 In the V-I-R triangle, how do we find R? (a) R = V × I (b) R = V ÷ I (c) R = V + I (d) R = I ÷ V
10. 10.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) bigger (c) smaller (d) zero
11. 11.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) the size of a cell (d) energy used each second
12. 12.🔺 A current of 40 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
13. 13.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to store charge (c) to limit the current (d) to make it brighter
14. 14.🌈 In the resistor colour code, which number does black stand for?
15. 15.🌈 In the resistor colour code, which number does grey stand for?
16. 16.🧩 Which component stores a little charge? (a) motor (b) thermistor (c) capacitor (d) resistor
17. 17.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 0 % (c) 25 % (d) 5 %
18. 18.What does a transistor do? (a) lets current go one way (b) senses how hot it is (c) has coloured bands (d) boosts a small signal
19. 19.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) True (b) False
20. 20.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
21. 21.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3.5 V supply. What current flows (in mA)?
22. 22.🔺 A current of 3 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
23. 23.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V ÷ I (d) P = V × I
24. 24.⚡ A device works on 3 V and takes 0.1 A. What is its power (in watts)? =
25. 25.🧮 Two resistors in parallel give a total that is … (a) their sum (b) always zero (c) less than either one (d) more than either one
26. 26.🧮 Resistors of 470 Ω, 220 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
27. 27.🌈 A resistor has the colour bands green, black, black. What is its value (in ohms)?
28. 28.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) gets smaller (d) becomes zero
29. 29.True or false: on an LED, the leg by the flat edge is the anode (+). (a) True (b) False
30. 30.🧾 A 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 7 hours. How many watt-hours (Wh) are saved?
31. 31.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
32. 32.⚡ A device works on 3 V and takes 1 A. What is its power (in watts)? =
33. 33.True or false: the flow of charge is measured in amperes (A). (a) False (b) True
34. 34.🔺 A 12.5 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
35. 35.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the water pressure (c) the flow of water (d) a bigger tank
36. 36.What does a potentiometer do? (a) has coloured bands (b) senses how hot it is (c) beeps for an alarm (d) is a resistance knob
37. 37.True or false: current is measured in ohms (Ω). (a) True (b) False
38. 38.🔺 A current of 0.2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
39. 39.🌈 A resistor has the colour bands green, brown, yellow. What is its value in kilo-ohms (kΩ)? =
40. 40.🔺 A 1 V supply is joined across a 100 Ω resistor. What current flows (in milliamperes, mA)?

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