Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 18 · 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.True or false: current is measured in watts (W). (a) False (b) True
2. 2.🧮 Resistors of 470 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
3. 3.📏 How many amperes (A) is 2840 mA? =
4. 4.🔺 A current of 20 mA flows when 4.4 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
6. 6.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a resistor (c) a capacitor (d) a diode
7. 7.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
8. 8.🔺 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
9. 9.🌈 A resistor has the colour bands orange, black, red. What is its value (in ohms)?
10. 10.🧩 Which part changes electrical energy into movement? (a) a motor (b) a fuse (c) a resistor (d) an LED
11. 11.⚡ A 1.5 W device works on 1.5 V. What current does it take (in amperes)? =
12. 12.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
13. 13.💡 What happens if an LED is put in backwards? (a) it does not light (b) it lights brighter (c) it changes colour (d) it makes a sound
14. 14.🧩 Which component beeps for an alarm? (a) LDR (b) potentiometer (c) capacitor (d) buzzer
15. 15.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
16. 16.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
17. 17.🔺 A current of 1 A flows when 5 V is joined across a resistor. What is its resistance (in ohms)?
18. 18.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) smaller (c) stay the same (d) zero
19. 19.Which of these saves electricity? (a) run fans in empty rooms (b) iron one shirt at a time (c) unplug idle chargers (d) leave the TV on standby
20. 20.💡 Why does an LED need a resistor in series? (a) to limit the current (b) to store charge (c) to make it brighter (d) to change its colour
21. 21.🧩 Which component senses how hot it is? (a) transistor (b) motor (c) thermistor (d) resistor
22. 22.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
23. 23.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
24. 24.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 210 Ω resistor? (a) red-brown-red (b) brown-red-brown (c) red-brown-black (d) red-brown-brown
25. 25.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 3.5 V supply. What current flows (in mA)?
26. 26.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
27. 27.True or false: the ammeter measures current. (a) True (b) False
28. 28.🌈 In the resistor colour code, which number does blue stand for?
29. 29.⚡ A 0.75 W device works on 1.5 V. What current does it take (in amperes)? =
30. 30.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 25 % (c) 5 % (d) 0 %
31. 31.🔺 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
32. 32.🔺 A current of 20 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
33. 33.🌈 A resistor has the colour bands orange, brown, brown. What is its value (in ohms)?
34. 34.🌈 A resistor has the colour bands red, green, black. What is its value (in ohms)?
35. 35.Which of these is measured in amperes (A)? (a) current (b) voltage (c) the push of a cell (d) energy used each second
36. 36.🧮 A 68 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)?
37. 37.📏 How many kilowatts (kW) is 1250 W? =
38. 38.True or false: the ammeter is joined in series. (a) False (b) True
39. 39.🧮 A 2.25 V battery is joined to 3 Ω and 6 Ω resistors in series. What current flows (in amperes)? =
40. 40.What does a thermistor do? (a) limits the current (b) senses how bright it is (c) senses how hot it is (d) glows using little power

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