Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 527 · 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 is the odd one out? (a) close the fridge quickly (b) leave the TV on standby (c) switch off empty rooms (d) set the AC to 24 °C
2. 2.💡 Does it save or waste electricity to switch off empty rooms? (a) wastes electricity (b) saves electricity
3. 3.Which of these wastes electricity? (a) unplug idle chargers (b) run fans in empty rooms (c) use LED lamps (d) use daylight to read
4. 4.True or false: to close the fridge quickly saves electricity. (a) True (b) False
5. 5.⚡ Power tells us … (a) the length of a wire (b) energy used each second (c) the size of a cell (d) the colour of light
6. 6.🔺 A current of 40 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) always zero (c) less than either one (d) their sum
8. 8.🧩 A capacitor in a circuit can … (a) spin a wheel (b) measure heat (c) store charge briefly (d) make light
9. 9.🧮 Resistors of 100 Ω, 22 Ω, 470 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
10. 10.What does a fuse do? (a) senses how hot it is (b) is a resistance knob (c) limits the current (d) blows if current is high
11. 11.⚡ A 12 W device works on 12 V. What current does it take (in amperes)? =
12. 12.🧮 A 2.5 V battery is joined to 4 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
13. 13.🔺 A current of 40 mA flows when 18.8 V is joined across a resistor. What is its resistance (in ohms)?
14. 14.🔺 A current of 2.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
15. 15.What does a buzzer do? (a) limits the current (b) glows using little power (c) has coloured bands (d) makes a beeping sound
16. 16.True or false: a resistor limits the current. (a) False (b) True
17. 17.🧩 Which component turns a fan or wheels? (a) LDR (b) fuse (c) motor (d) buzzer
18. 18.🔺 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
19. 19.🔺 A current of 25 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
20. 20.📏 How many ohms (Ω) is 4.9 kΩ?
21. 21.🔺 A current of 2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
22. 22.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V + I (d) P = V ÷ I
23. 23.🔺 A current of 3 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
24. 24.🔺 A current of 20 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
25. 25.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
26. 26.🧩 Which component has coloured bands? (a) potentiometer (b) fuse (c) resistor (d) buzzer
27. 27.True or false: the ammeter is joined in series. (a) False (b) True
28. 28.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) the flow of water (c) a narrow pipe (d) the pipe colour
29. 29.🔺 A current of 2.5 A flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
30. 30.What does a motor do? (a) stores a little charge (b) makes things spin (c) glows using little power (d) senses how bright it is
31. 31.🧮 A 1.2 V battery is joined to 2 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
32. 32.True or false: voltage is measured in volts (V). (a) False (b) True
33. 33.🔺 A 30 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
34. 34.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
35. 35.💡 Does it save or waste electricity to use LED lamps? (a) saves electricity (b) wastes electricity
36. 36.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it changes colour (d) it does not light
37. 37.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 100 (c) 60 (d) 1000
38. 38.🧩 Which component beeps for an alarm? (a) fuse (b) capacitor (c) LED (d) buzzer
39. 39.Which of these is measured in amperes (A)? (a) resistance (b) the push of a cell (c) current (d) voltage
40. 40.📏 How many watts (W) is 4.9 kW?

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