Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 122 · 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 gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 50 % (c) 0 % (d) 5 %
2. 2.💡 A blue LED uses 3 V and should get 10 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
3. 3.💡 Does it save or waste electricity to iron one shirt at a time? (a) wastes electricity (b) saves electricity
4. 4.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
5. 5.⚡ Which formula gives electric power? (a) P = I ÷ V (b) P = V × I (c) P = V ÷ I (d) P = V + I
6. 6.⚡ A device works on 12 V and takes 0.1 A. What is its power (in watts)? =
7. 7.True or false: on an LED, the leg by the flat edge is the anode (+). (a) False (b) True
8. 8.🌈 In the resistor colour code, which number does grey stand for?
9. 9.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
10. 10.🔺 A current of 20 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
11. 11.Which of these is measured in volts (V)? (a) energy used each second (b) how much a part resists (c) the flow of charge (d) voltage
12. 12.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) smaller (c) stay the same (d) bigger
13. 13.What does a buzzer do? (a) has coloured bands (b) lets current go one way (c) makes a beeping sound (d) stores a little charge
14. 14.💡 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)?
15. 15.🔺 A 25 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
16. 16.🧩 Which component turns a fan or wheels? (a) LDR (b) motor (c) transistor (d) potentiometer
17. 17.📏 How many milliamperes (mA) is 2.79 A?
18. 18.🔺 In the V-I-R triangle, how do we find I? (a) I = R ÷ V (b) I = V × R (c) I = V + R (d) I = V ÷ R
19. 19.🌈 A resistor has the colour bands brown, orange, yellow. What is its value in kilo-ohms (kΩ)? =
20. 20.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 6600 Ω resistor? (a) blue-violet-red (b) blue-blue-orange (c) blue-blue-brown (d) blue-blue-red
21. 21.True or false: a diode glows using little power. (a) True (b) False
22. 22.🧮 Resistors of 470 Ω, 47 Ω, 10 Ω and 330 Ω are joined in series. What is the total resistance (in ohms)?
23. 23.True or false: a potentiometer is a resistance knob. (a) False (b) True
24. 24.🔺 A current of 50 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
25. 25.🧮 A 470 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)?
26. 26.True or false: a buzzer beeps for an alarm. (a) True (b) False
27. 27.🔺 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
28. 28.🌈 In the resistor colour code, which number does blue stand for?
29. 29.🔺 A 1 V supply is joined across a 4 Ω resistor. What current flows (in amperes)? =
30. 30.Which of these wastes electricity? (a) close the fridge quickly (b) use LED lamps (c) use daylight to read (d) run fans in empty rooms
31. 31.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 85000 Ω resistor? (a) grey-green-red (b) grey-green-yellow (c) green-grey-orange (d) grey-green-orange
32. 32.🧮 Resistors of 50 Ω and 20 Ω are joined in series. What is the total resistance (in ohms)?
33. 33.💡 Does it save or waste electricity to set the AC to 24 °C? (a) wastes electricity (b) saves electricity
34. 34.What does a motor do? (a) glows using little power (b) makes things spin (c) has coloured bands (d) stores a little charge
35. 35.True or false: an LDR senses how bright it is. (a) False (b) True
36. 36.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
37. 37.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
38. 38.📏 How many milliamperes (mA) is 1.68 A?
39. 39.🧩 Which component boosts a small signal? (a) transistor (b) buzzer (c) LED (d) potentiometer
40. 40.🧮 A 47 Ω resistor is joined in series with two equal 100 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?

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