Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 973 · 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.⚡ Power tells us … (a) the colour of light (b) the length of a wire (c) the size of a cell (d) energy used each second
2. 2.🧮 A 2 V battery is joined to 10 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
3. 3.🔺 A current of 50 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
4. 4.💡 Does it save or waste electricity to switch off empty rooms? (a) saves electricity (b) wastes electricity
5. 5.🔺 A current of 25 mA flows when 2.5 V is joined across a resistor. What is its resistance (in ohms)?
6. 6.📏 Voltmeter or ammeter: which one is joined across a part? (a) ammeter (b) voltmeter
7. 7.🌈 In the resistor colour code, which number does black stand for?
8. 8.🧩 Which component makes things spin? (a) fuse (b) motor (c) thermistor (d) transistor
9. 9.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it makes a sound (c) it changes colour (d) it does not light
10. 10.True or false: a fuse is a resistance knob. (a) False (b) True
11. 11.🔺 A 1.5 V supply is joined across a 3 Ω resistor. What current flows (in amperes)? =
12. 12.⚡ A device works on 1.5 V and takes 1.5 A. What is its power (in watts)? =
13. 13.🧩 A capacitor in a circuit can … (a) make light (b) spin a wheel (c) measure heat (d) store charge briefly
14. 14.💡 An LED is joined to a 6 V battery with no resistor; its long leg goes to the + side and its short leg to the − side. What happens? (a) does not light (b) lights up (c) may burn out
15. 15.True or false: on an LED, the shorter leg is the cathode (−). (a) False (b) True
16. 16.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) bigger (c) smaller (d) stay the same
17. 17.🌈 A resistor has the colour bands red, blue, orange. What is its value in kilo-ohms (kΩ)? =
18. 18.🔺 A current of 10 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🌈 A gold fourth band on a resistor means the value may be off by … (a) 50 % (b) 5 % (c) 0 % (d) 25 %
20. 20.🌈 Which band is read first on a resistor? (a) the widest gap (b) the gold band (c) the one nearest an end (d) any band
21. 21.What does an LDR do? (a) senses how hot it is (b) limits the current (c) lets current go one way (d) senses how bright it is
22. 22.⚡ A 1 W device works on 5 V. What current does it take (in amperes)? =
23. 23.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
24. 24.📏 In the water-pipe picture of a circuit, resistance is like … (a) a narrow pipe (b) a bigger tank (c) the water pressure (d) the flow of water
25. 25.🧮 Resistors of 10 Ω and 50 Ω are joined in series. What is the total resistance (in ohms)?
26. 26.True or false: the ammeter measures current. (a) False (b) True
27. 27.🧩 Which component senses how hot it is? (a) thermistor (b) fuse (c) LDR (d) potentiometer
28. 28.📏 Which unit measures resistance? (a) watt (W) (b) ampere (A) (c) volt (V) (d) ohm (Ω)
29. 29.🔺 A 2 V supply is joined across a 200 Ω resistor. What current flows (in milliamperes, mA)?
30. 30.🔍 Which is the odd one out? (a) use old filament bulbs (b) use LED lamps (c) iron one shirt at a time (d) run fans in empty rooms
31. 31.🧾 A 75 W filament bulb is swapped for a 12 W LED lamp that gives about the same light. Both would run for 5 hours. How many watt-hours (Wh) are saved?
32. 32.True or false: the ammeter is joined across a part. (a) True (b) False
33. 33.💡 On an LED, is the round-side leg the anode (+) or the cathode (−)? (a) cathode (−) (b) anode (+)
34. 34.⚡ A device works on 1.5 V and takes 0.25 A. What is its power (in watts)? =
35. 35.⚡ A home appliance on the 230 V mains takes 5 A. What is its power (in watts)?
36. 36.🧩 Which component limits the current? (a) thermistor (b) resistor (c) LED (d) capacitor
37. 37.🧾 Which lamp gives the same light for the least power? (a) a filament bulb (b) a candle (c) an oil lamp (d) an LED lamp
38. 38.💡 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?
39. 39.🔺 In the V-I-R triangle, how do we find V? (a) V = I ÷ R (b) V = R ÷ I (c) V = I + R (d) V = I × R
40. 40.True or false: to use daylight to read saves electricity. (a) True (b) False

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