Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 46 · 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: how much a part resists is measured in ohms (Ω). (a) True (b) False
2. 2.🔺 A current of 0.2 A flows through a 3 Ω resistor. What is the voltage across it (in volts)? =
3. 3.🔺 A current of 0.25 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
4. 4.🔺 A current of 1.5 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
5. 5.🔺 A current of 10 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
6. 6.🌈 In the resistor colour code, which number does violet stand for?
7. 7.🔺 A current of 0.2 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
8. 8.⚡ A device works on 5 V and takes 1.5 A. What is its power (in watts)? =
9. 9.🌈 A resistor has the colour bands green, orange, red. What is its value in kilo-ohms (kΩ)? =
10. 10.🔺 An 18 V supply is joined across a 6 Ω resistor. What current flows (in amperes)? =
11. 11.True or false: the ammeter measures current. (a) True (b) False
12. 12.🔺 A 5 V supply is joined across a 2 Ω resistor. What current flows (in amperes)? =
13. 13.🔺 A current of 0.1 A flows through a 15 Ω resistor. What is the voltage across it (in volts)? =
14. 14.📏 In the water-pipe picture of a circuit, resistance is like … (a) the water pressure (b) a narrow pipe (c) the flow of water (d) a bigger tank
15. 15.True or false: a resistor senses how bright it is. (a) True (b) False
16. 16.⚡ A device works on 24 V and takes 1 A. What is its power (in watts)? =
17. 17.What does a potentiometer do? (a) senses how hot it is (b) turns a fan or wheels (c) blows if current is high (d) is a resistance knob
18. 18.🧩 Which component limits the current? (a) LED (b) thermistor (c) motor (d) resistor
19. 19.Which of these is measured in watts (W)? (a) how much a part resists (b) power (c) voltage (d) the push of a cell
20. 20.🔺 A current of 25 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
21. 21.True or false: on an LED, the longer leg is the cathode (−). (a) True (b) False
22. 22.🌈 Which band is read first on a resistor? (a) the gold band (b) the widest gap (c) any band (d) the one nearest an end
23. 23.🌈 A resistor has the colour bands green, grey, orange. What is its value (in ohms)?
24. 24.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 94 Ω resistor? (a) yellow-white-black (b) white-yellow-black (c) white-yellow-brown (d) brown-yellow-black
25. 25.🧮 Five equal 125 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🔺 A 7.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
27. 27.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
28. 28.True or false: an LDR senses how bright it is. (a) True (b) False
29. 29.What does an LDR do? (a) boosts a small signal (b) senses how bright it is (c) stores a little charge (d) has coloured bands
30. 30.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark a 32 Ω resistor? (a) yellow-red-black (b) orange-red-brown (c) orange-red-black (d) red-orange-black
31. 31.🧩 A capacitor in a circuit can … (a) make light (b) store charge briefly (c) measure heat (d) spin a wheel
32. 32.📏 In the water-pipe picture of a circuit, current is like … (a) a narrow pipe (b) the pipe colour (c) the water pressure (d) the flow of water
33. 33.🌈 A resistor has the colour bands blue, green, red. What is its value in kilo-ohms (kΩ)? =
34. 34.True or false: the ammeter is joined across a part. (a) False (b) True
35. 35.🧮 Adding another resistor in series makes the total resistance … (a) stay the same (b) zero (c) bigger (d) smaller
36. 36.Which of these is measured in amperes (A)? (a) energy used each second (b) voltage (c) the flow of charge (d) power
37. 37.🔺 A current of 25 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
38. 38.🔺 A 3 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
39. 39.💡 A red LED (it uses 2 V) is joined with a 200 Ω resistor to a 3 V supply. What current flows (in mA)?
40. 40.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True

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