Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 455 · 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 red LED (it uses 2 V) is joined with a 150 Ω resistor to a 4.25 V supply. What current flows (in mA)?
2. 2.True or false: a resistor limits the current. (a) False (b) True
3. 3.🧮 Four equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
4. 4.🌈 In the resistor colour code, which number does white stand for?
5. 5.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a capacitor (c) a diode (d) a resistor
6. 6.🧮 Resistors of 50 Ω, 20 Ω and 100 Ω are joined in series. What is the total resistance (in ohms)?
7. 7.💡 Does it save or waste electricity to use old filament bulbs? (a) saves electricity (b) wastes electricity
8. 8.🔺 In the V-I-R triangle, how do we find R? (a) R = I ÷ V (b) R = V + I (c) R = V ÷ I (d) R = V × I
9. 9.🌈 In the resistor colour code, which number does violet stand for?
10. 10.🔺 A 12 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
11. 11.🔺 A current of 2 A flows when 20 V is joined across a resistor. What is its resistance (in ohms)?
12. 12.True or false: a potentiometer senses how bright it is. (a) True (b) False
13. 13.🧮 A 20 Ω resistor is joined in series with two equal 1000 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
14. 14.Which of these is measured in volts (V)? (a) how much a part resists (b) energy used each second (c) resistance (d) voltage
15. 15.🧾 A 100 W appliance runs for 6 hours. How many units (kWh) of electricity does it use? =
16. 16.🧮 A 22 Ω resistor is joined in series with two equal 10 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
17. 17.📏 In the water-pipe picture of a circuit, voltage is like … (a) the tap handle (b) the water pressure (c) the water tank lid (d) the pipe colour
18. 18.🌈 In the resistor colour code, which number does black stand for?
19. 19.🌈 A gold fourth band on a resistor means the value may be off by … (a) 0 % (b) 25 % (c) 5 % (d) 50 %
20. 20.📏 How many amperes (A) is 2700 mA? =
21. 21.🌈 A resistor has the colour bands grey, white, red. What is its value in kilo-ohms (kΩ)? =
22. 22.True or false: resistance is measured in watts (W). (a) True (b) False
23. 23.📏 How many watts (W) is 4 kW?
24. 24.💡 Does it save or waste electricity to leave the TV on standby? (a) saves electricity (b) wastes electricity
25. 25.📏 How many amperes (A) is 1570 mA? =
26. 26.📏 How many milliamperes (mA) make 1 ampere? (a) 10 (b) 100 (c) 60 (d) 1000
27. 27.🧩 Which component senses how hot it is? (a) LDR (b) buzzer (c) capacitor (d) thermistor
28. 28.What does a motor do? (a) turns a fan or wheels (b) senses how bright it is (c) has coloured bands (d) smooths a wobbly supply
29. 29.💡 A red LED (it uses 2 V) is joined with a 150 Ω resistor to a 5 V supply. What current flows (in mA)?
30. 30.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 29 Ω resistor? (a) red-white-black (b) red-white-brown (c) orange-white-black (d) white-red-black
31. 31.🧩 A capacitor in a circuit can … (a) spin a wheel (b) make light (c) measure heat (d) store charge briefly
32. 32.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) an oil lamp (c) an LED lamp (d) a candle
33. 33.🧩 Which component limits the current? (a) buzzer (b) resistor (c) potentiometer (d) motor
34. 34.🔺 A 1 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
35. 35.True or false: a buzzer turns a fan or wheels. (a) True (b) False
36. 36.🧮 A 7.5 V battery is joined to 10 Ω and 5 Ω resistors in series. What current flows (in amperes)? =
37. 37.🧮 Four equal 400 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
38. 38.What does a fuse do? (a) blows if current is high (b) boosts a small signal (c) has coloured bands (d) limits the current
39. 39.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) an LED (d) a fuse
40. 40.⚡ A device works on 9 V and takes 0.1 A. What is its power (in watts)? =

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