Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 630 · 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.🌈 In the resistor colour code, which number does brown stand for?
2. 2.🧾 A 200 W appliance runs for 8 hours. How many units (kWh) of electricity does it use? =
3. 3.🧾 A 50 W appliance runs for 5 hours. How many units (kWh) of electricity does it use? =
4. 4.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) the gold band (d) any band
5. 5.What does a resistor do? (a) makes a beeping sound (b) blows if current is high (c) makes things spin (d) limits the current
6. 6.🧮 Two equal 1000 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
7. 7.⚡ Power tells us … (a) the size of a cell (b) energy used each second (c) the colour of light (d) the length of a wire
8. 8.🔺 In the V-I-R triangle, how do we find I? (a) I = V + R (b) I = R ÷ V (c) I = V ÷ R (d) I = V × R
9. 9.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
10. 10.🧮 A 10 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
11. 11.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
12. 12.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 81000 Ω resistor? (a) grey-brown-yellow (b) grey-brown-red (c) brown-grey-orange (d) grey-brown-orange
13. 13.🔺 A current of 2.5 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
14. 14.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
15. 15.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 4200 Ω resistor? (a) red-yellow-red (b) yellow-red-orange (c) yellow-red-red (d) yellow-red-brown
16. 16.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) becomes zero (b) gets smaller (c) gets bigger (d) stays the same
17. 17.What does a buzzer do? (a) has coloured bands (b) is a resistance knob (c) makes a beeping sound (d) smooths a wobbly supply
18. 18.💡 A red LED uses 2 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
19. 19.⚡ A device works on 9 V and takes 0.5 A. What is its power (in watts)? =
20. 20.📏 In the water-pipe picture of a circuit, voltage is like … (a) the water pressure (b) the pipe colour (c) the tap handle (d) the water tank lid
21. 21.🔺 A 20 V supply is joined across a 20 Ω resistor. What current flows (in amperes)? =
22. 22.🔺 A 7.5 V supply is joined across a 300 Ω resistor. What current flows (in milliamperes, mA)?
23. 23.🧮 Five equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
24. 24.🔺 A current of 0.2 A flows when 4 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
26. 26.⚡ Which formula gives electric power? (a) P = V × I (b) P = V ÷ I (c) P = I ÷ V (d) P = V + I
27. 27.📏 How many amperes (A) is 2940 mA? =
28. 28.🔺 A current of 25 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
29. 29.🧾 A 100 W filament bulb is swapped for a 15 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
30. 30.🔺 A current of 20 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
31. 31.True or false: a motor senses how bright it is. (a) True (b) False
32. 32.🔺 A current of 3 A flows when 6 V is joined across a resistor. What is its resistance (in ohms)?
33. 33.🧮 Resistors of 20 Ω, 20 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
34. 34.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) stay the same (d) bigger
35. 35.📏 Which unit measures energy used each second? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
36. 36.💡 What happens if an LED is put in backwards? (a) it makes a sound (b) it does not light (c) it changes colour (d) it lights brighter
37. 37.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) the water pressure (c) the flow of water (d) a bigger tank
38. 38.Which of these is measured in ohms (Ω)? (a) voltage (b) resistance (c) current (d) power
39. 39.🧩 Which component limits the current? (a) diode (b) capacitor (c) motor (d) resistor
40. 40.🧮 Four equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?

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