Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 130 · 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 component smooths a wobbly supply? (a) resistor (b) buzzer (c) capacitor (d) LDR
2. 2.What does a capacitor do? (a) has coloured bands (b) smooths a wobbly supply (c) makes things spin (d) beeps for an alarm
3. 3.📏 How many milliamperes (mA) make 1 ampere? (a) 60 (b) 1000 (c) 10 (d) 100
4. 4.🧩 Which component makes a beeping sound? (a) buzzer (b) thermistor (c) LDR (d) resistor
5. 5.🔍 Which is the odd one out? (a) unplug idle chargers (b) use LED lamps (c) use old filament bulbs (d) use daylight to read
6. 6.🧮 A 2 V battery is joined to 8 Ω and 12 Ω resistors in series. What current flows (in amperes)? =
7. 7.🔺 A current of 2.5 A flows through a 2 Ω resistor. What is the voltage across it (in volts)? =
8. 8.True or false: a motor senses how hot it is. (a) False (b) True
9. 9.🔺 In the V-I-R triangle, how do we find I? (a) I = V ÷ R (b) I = V + R (c) I = V × R (d) I = R ÷ V
10. 10.True or false: on an LED, the round-side leg is the cathode (−). (a) False (b) True
11. 11.⚡ A device works on 6 V and takes 0.25 A. What is its power (in watts)? =
12. 12.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
13. 13.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
14. 14.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
15. 15.📏 In the water-pipe picture of a circuit, voltage is like … (a) the pipe colour (b) the water tank lid (c) the tap handle (d) the water pressure
16. 16.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
17. 17.🧩 Which part changes electrical energy into movement? (a) a resistor (b) a fuse (c) a motor (d) an LED
18. 18.🌈 A resistor has the colour bands brown, blue, red. What is its value (in ohms)?
19. 19.🔺 In the V-I-R triangle, how do we find V? (a) V = R ÷ I (b) V = I + R (c) V = I × R (d) V = I ÷ R
20. 20.🧩 Which component blows if current is high? (a) transistor (b) LED (c) LDR (d) fuse
21. 21.🔺 A 0.6 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
22. 22.🧾 A 100 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
23. 23.Which of these is measured in volts (V)? (a) the push of a cell (b) resistance (c) the flow of charge (d) current
24. 24.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4800 Ω resistor? (a) yellow-grey-orange (b) yellow-grey-brown (c) yellow-grey-red (d) grey-yellow-red
25. 25.🔺 A current of 50 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
26. 26.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
27. 27.What does an LED do? (a) makes things spin (b) senses how hot it is (c) limits the current (d) glows using little power
28. 28.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a resistor (c) a capacitor (d) a diode
29. 29.📏 Which unit measures power? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
30. 30.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
31. 31.🔺 A current of 25 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
32. 32.Which of these saves electricity? (a) use old filament bulbs (b) switch off empty rooms (c) iron one shirt at a time (d) leave the TV on standby
33. 33.Which of these wastes electricity? (a) close the fridge quickly (b) run fans in empty rooms (c) switch off empty rooms (d) set the AC to 24 °C
34. 34.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
35. 35.📏 In the water-pipe picture of a circuit, current is like … (a) a narrow pipe (b) the pipe colour (c) the water pressure (d) the flow of water
36. 36.⚡ Power tells us … (a) the size of a cell (b) the colour of light (c) energy used each second (d) the length of a wire
37. 37.What does a fuse do? (a) beeps for an alarm (b) turns a fan or wheels (c) stores a little charge (d) blows if current is high
38. 38.🔺 A 37.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
39. 39.⚡ A device works on 9 V and takes 0.25 A. What is its power (in watts)? =
40. 40.💡 A red LED uses 2 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?

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