Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 905 · 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.🔺 A 1.5 V supply is joined across a 15 Ω resistor. What current flows (in amperes)? =
2. 2.True or false: on an LED, the longer leg is the cathode (−). (a) False (b) True
3. 3.What does an LDR do? (a) glows using little power (b) smooths a wobbly supply (c) senses how bright it is (d) has coloured bands
4. 4.📏 Which unit measures energy used each second? (a) ohm (Ω) (b) ampere (A) (c) watt (W) (d) volt (V)
5. 5.🧩 Which part changes electrical energy into movement? (a) a motor (b) a fuse (c) a resistor (d) an LED
6. 6.Which of these is measured in ohms (Ω)? (a) power (b) how much a part resists (c) energy used each second (d) the flow of charge
7. 7.🌈 A resistor has the colour bands yellow, yellow, brown. What is its value (in ohms)?
8. 8.📏 Voltmeter or ammeter: which one measures voltage? (a) voltmeter (b) ammeter
9. 9.🔺 A current of 1.5 A flows when 18 V is joined across a resistor. What is its resistance (in ohms)?
10. 10.🔺 A current of 10 mA flows through a 150 Ω resistor. What is the voltage across it (in volts)? =
11. 11.💡 An LED is joined to a 5 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
12. 12.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
13. 13.🧾 A 500 W appliance runs for 2 hours. How many units (kWh) of electricity does it use? =
14. 14.True or false: on an LED, the longer leg is the anode (+). (a) False (b) True
15. 15.🧮 Adding another resistor in series makes the total resistance … (a) zero (b) stay the same (c) bigger (d) smaller
16. 16.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to a 6.5 V supply. What current flows (in mA)?
17. 17.🧾 A 40 W filament bulb is swapped for a 6 W LED lamp that gives about the same light. Both would run for 6 hours. How many watt-hours (Wh) are saved?
18. 18.🧮 Two resistors in parallel give a total that is … (a) always zero (b) more than either one (c) less than either one (d) their sum
19. 19.📏 How many milliamperes (mA) is 0.57 A?
20. 20.🌈 Which band is read first on a resistor? (a) any band (b) the widest gap (c) the one nearest an end (d) the gold band
21. 21.💡 Does it save or waste electricity to leave fridge door open? (a) saves electricity (b) wastes electricity
22. 22.🌈 A resistor has the colour bands blue, black, brown. What is its value (in ohms)?
23. 23.📏 How many kilowatts (kW) is 4900 W? =
24. 24.🔺 A current of 2.5 A flows when 50 V is joined across a resistor. What is its resistance (in ohms)?
25. 25.💡 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
26. 26.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.🔺 A current of 2 A flows when 8 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.🔍 Which is the odd one out? (a) use LED lamps (b) run fans in empty rooms (c) iron one shirt at a time (d) leave fridge door open
29. 29.💡 A red LED (it uses 2 V) is joined with a 300 Ω resistor to an 8 V supply. What current flows (in mA)?
30. 30.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
31. 31.🌈 In the resistor colour code, which number does white stand for?
32. 32.True or false: a capacitor stores a little charge. (a) False (b) True
33. 33.🌈 A resistor has the colour bands grey, black, black. What is its value (in ohms)?
34. 34.🔺 A current of 0.25 A flows when 3.75 V is joined across a resistor. What is its resistance (in ohms)?
35. 35.🧩 A capacitor in a circuit can … (a) spin a wheel (b) measure heat (c) make light (d) store charge briefly
36. 36.🌈 In the resistor colour code, which number does violet stand for?
37. 37.💡 A red LED uses 2 V and should get 25 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
38. 38.🧮 Two equal 200 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
39. 39.🧩 Which component makes a beeping sound? (a) buzzer (b) diode (c) thermistor (d) fuse
40. 40.🔺 A 10 V supply is joined across a 250 Ω resistor. What current flows (in milliamperes, mA)?

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