Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 66 · 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.📏 How many ohms make 1 kilo-ohm (kΩ)? (a) 1000 (b) 1024 (c) 100 (d) 10
2. 2.True or false: resistance is measured in ohms (Ω). (a) False (b) True
3. 3.🧮 Resistors of 470 Ω, 33 Ω and 47 Ω are joined in series. What is the total resistance (in ohms)?
4. 4.🌈 In the resistor colour code, which number does brown stand for?
5. 5.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
6. 6.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
7. 7.⚡ A device works on 6 V and takes 2 A. What is its power (in watts)? =
8. 8.🔍 Which is the odd one out? (a) leave the TV on standby (b) use old filament bulbs (c) use daylight to read (d) iron one shirt at a time
9. 9.🔺 A 20 V supply is joined across a 500 Ω resistor. What current flows (in milliamperes, mA)?
10. 10.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) less than either one (c) their sum (d) always zero
11. 11.🔺 A current of 3 A flows when 45 V is joined across a resistor. What is its resistance (in ohms)?
12. 12.True or false: to set the AC to 24 °C saves electricity. (a) False (b) True
13. 13.🔺 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
14. 14.🌈 In the resistor colour code, which number does orange stand for?
15. 15.🧩 Which part changes electrical energy into movement? (a) a motor (b) a resistor (c) an LED (d) a fuse
16. 16.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 11 Ω resistor? (a) brown-brown-brown (b) red-brown-black (c) brown-brown-black (d) brown-red-black
17. 17.🌈 A gold fourth band on a resistor means the value may be off by … (a) 25 % (b) 0 % (c) 5 % (d) 50 %
18. 18.What does a diode do? (a) limits the current (b) beeps for an alarm (c) lets current go one way (d) smooths a wobbly supply
19. 19.📏 How many amperes (A) is 300 mA? =
20. 20.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
21. 21.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
22. 22.🔺 A current of 20 mA flows through a 330 Ω resistor. What is the voltage across it (in volts)? =
23. 23.🔺 A current of 2 A flows through a 10 Ω resistor. What is the voltage across it (in volts)? =
24. 24.⚡ Power tells us … (a) the colour of light (b) energy used each second (c) the size of a cell (d) the length of a wire
25. 25.🔺 A current of 50 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
26. 26.📏 How many milliamperes (mA) is 0.72 A?
27. 27.💡 Does it save or waste electricity to leave the TV on standby? (a) wastes electricity (b) saves electricity
28. 28.🧩 Which part changes electrical energy into sound? (a) a buzzer (b) a capacitor (c) a resistor (d) a diode
29. 29.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
30. 30.🌈 Which band is read first on a resistor? (a) the widest gap (b) the one nearest an end (c) any band (d) the gold band
31. 31.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
32. 32.💡 An LED is joined to a 3 V battery through a 470 Ω resistor; the leg next to the flat edge of its rim goes to the + side. What happens? (a) may burn out (b) lights up (c) does not light
33. 33.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
34. 34.🔺 A current of 1.5 A flows when 4.5 V is joined across a resistor. What is its resistance (in ohms)?
35. 35.🔺 An 8.8 V supply is joined across a 220 Ω resistor. What current flows (in milliamperes, mA)?
36. 36.True or false: the ammeter measures current. (a) False (b) True
37. 37.🧮 Adding another resistor in series makes the total resistance … (a) smaller (b) zero (c) bigger (d) stay the same
38. 38.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.📏 In the water-pipe picture of a circuit, current is like … (a) the water pressure (b) a narrow pipe (c) the flow of water (d) the pipe colour
40. 40.🔺 A current of 50 mA flows when 5 V is joined across a resistor. What is its resistance (in ohms)?

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