Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 805 · 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: on an LED, the longer leg is the cathode (−). (a) True (b) False
2. 2.💡 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
3. 3.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
4. 4.True or false: power is measured in volts (V). (a) False (b) True
5. 5.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 ampere (c) 1 kilowatt-hour (kWh) (d) 1 volt
6. 6.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 0 % (d) 25 %
7. 7.What does an LDR do? (a) boosts a small signal (b) smooths a wobbly supply (c) senses how bright it is (d) blows if current is high
8. 8.True or false: a motor turns a fan or wheels. (a) False (b) True
9. 9.📏 Which unit measures the flow of charge? (a) ampere (A) (b) watt (W) (c) ohm (Ω) (d) volt (V)
10. 10.🌈 A resistor has the colour bands red, brown, brown. What is its value (in ohms)?
11. 11.🧮 Two equal 330 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
12. 12.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 3 V supply. What current flows (in mA)?
13. 13.🔺 A current of 20 mA flows when 3 V is joined across a resistor. What is its resistance (in ohms)?
14. 14.🧮 Adding another resistor in series makes the total resistance … (a) bigger (b) zero (c) stay the same (d) smaller
15. 15.🔍 Which is the odd one out? (a) use daylight to read (b) close the fridge quickly (c) iron one shirt at a time (d) use LED lamps
16. 16.🔺 A current of 0.1 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
17. 17.⚡ Power tells us … (a) energy used each second (b) the size of a cell (c) the length of a wire (d) the colour of light
18. 18.💡 What does LED stand for? (a) low energy device (b) light energy dial (c) large electric dial (d) light-emitting diode
19. 19.🧮 A 47 Ω resistor is joined in series with two equal 220 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
20. 20.🔺 A current of 1 A flows when 2 V is joined across a resistor. What is its resistance (in ohms)?
21. 21.🔺 A current of 50 mA flows when 7.5 V is joined across a resistor. What is its resistance (in ohms)?
22. 22.🔺 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
23. 23.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
24. 24.True or false: resistance is measured in watts (W). (a) True (b) False
25. 25.💡 A blue LED uses 3 V and should get 25 mA. It runs from a 12 V supply. What resistor (in ohms) is needed in series?
26. 26.🔺 A 15 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
27. 27.🧩 A capacitor in a circuit can … (a) measure heat (b) make light (c) store charge briefly (d) spin a wheel
28. 28.True or false: a resistor has coloured bands. (a) True (b) False
29. 29.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
30. 30.True or false: voltage is measured in volts (V). (a) False (b) True
31. 31.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 390 Ω resistor? (a) orange-white-black (b) white-orange-brown (c) orange-white-red (d) orange-white-brown
32. 32.🧮 A 6.5 V battery is joined to 5 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
33. 33.🔺 A 2 V supply is joined across an 8 Ω resistor. What current flows (in amperes)? =
34. 34.🌈 A resistor has the colour bands brown, grey, brown. What is its value (in ohms)?
35. 35.⚡ A home appliance on the 230 V mains takes 0.5 A. What is its power (in watts)?
36. 36.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
37. 37.💡 On an LED, is the leg by the flat edge the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
38. 38.🌈 A resistor has the colour bands white, violet, black. What is its value (in ohms)?
39. 39.🔺 A 7.5 V supply is joined across a 5 Ω resistor. What current flows (in amperes)? =
40. 40.🔺 A current of 20 mA flows when 6.6 V is joined across a resistor. What is its resistance (in ohms)?

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