Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 140 · 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.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) the one nearest an end (d) any band
2. 2.⚡ A 0.75 W device works on 3 V. What current does it take (in amperes)? =
3. 3.🔺 A 7.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
4. 4.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
5. 5.🔺 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
6. 6.🔺 A current of 0.1 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🔺 In the V-I-R triangle, how do we find R? (a) R = V ÷ I (b) R = I ÷ V (c) R = V × I (d) R = V + I
8. 8.🧮 A 150 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)?
9. 9.🧮 A 3.75 V battery is joined to 3 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
10. 10.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
11. 11.🔺 A current of 25 mA flows when 11.75 V is joined across a resistor. What is its resistance (in ohms)?
12. 12.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
13. 13.🔺 A current of 3 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
14. 14.🧩 Which component has coloured bands? (a) transistor (b) potentiometer (c) diode (d) resistor
15. 15.🧮 A 0.6 V battery is joined to 3 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
16. 16.True or false: the voltmeter measures voltage. (a) True (b) False
17. 17.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) bigger (c) zero (d) stay the same
18. 18.Which of these wastes electricity? (a) use LED lamps (b) use daylight to read (c) switch off empty rooms (d) run fans in empty rooms
19. 19.🧮 Two equal 470 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
20. 20.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
21. 21.💡 An LED is joined to a 6 V battery through a 470 Ω resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) may burn out (b) lights up (c) does not light
22. 22.🔺 A 30 V supply is joined across a 12 Ω resistor. What current flows (in amperes)? =
23. 23.True or false: to leave fridge door open saves electricity. (a) True (b) False
24. 24.🔺 A current of 3 A flows when 9 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the colour of light (d) the size of a cell
26. 26.True or false: to unplug idle chargers wastes electricity. (a) True (b) False
27. 27.True or false: to use daylight to read saves electricity. (a) False (b) True
28. 28.True or false: on an LED, the shorter leg is the anode (+). (a) True (b) False
29. 29.🧩 Which component makes a beeping sound? (a) buzzer (b) capacitor (c) thermistor (d) resistor
30. 30.🔺 A 1 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
31. 31.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
32. 32.⚡ Which formula gives electric power? (a) P = V + I (b) P = I ÷ V (c) P = V ÷ I (d) P = V × I
33. 33.⚡ A device works on 1.5 V and takes 0.1 A. What is its power (in watts)? =
34. 34.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
35. 35.🔺 A current of 1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
36. 36.True or false: an LED senses how bright it is. (a) True (b) False
37. 37.🔍 Which is the odd one out? (a) unplug idle chargers (b) leave the TV on standby (c) use daylight to read (d) set the AC to 24 °C
38. 38.📏 How many ohms (Ω) is 9.2 kΩ?
39. 39.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
40. 40.🧾 A 100 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =

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