Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 903 · 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 0.3 W device works on 3 V. What current does it take (in amperes)? =
2. 2.🔺 A current of 50 mA flows through a 300 Ω resistor. What is the voltage across it (in volts)? =
3. 3.Which of these is measured in ohms (Ω)? (a) resistance (b) the flow of charge (c) the push of a cell (d) current
4. 4.🌈 A resistor has the colour bands grey, blue, black. What is its value (in ohms)?
5. 5.🧮 Resistors of 33 Ω, 100 Ω, 100 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
6. 6.🔺 A current of 3 A flows through a 20 Ω resistor. What is the voltage across it (in volts)? =
7. 7.🔺 In the V-I-R triangle, how do we find R? (a) R = V + I (b) R = V × I (c) R = V ÷ I (d) R = I ÷ V
8. 8.🧩 Which part changes electrical energy into movement? (a) a resistor (b) a motor (c) an LED (d) a fuse
9. 9.🧮 Three equal 300 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
10. 10.🧮 Five equal 25 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
11. 11.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
12. 12.🧩 Which component lets current go one way? (a) LDR (b) fuse (c) diode (d) resistor
13. 13.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
14. 14.Which of these wastes electricity? (a) use old filament bulbs (b) close the fridge quickly (c) use daylight to read (d) set the AC to 24 °C
15. 15.💡 An LED is joined to a 5 V battery with no resistor; the leg next to the flat edge of its rim goes to the − side. What happens? (a) does not light (b) may burn out (c) lights up
16. 16.🔺 A current of 50 mA flows through a 400 Ω resistor. What is the voltage across it (in volts)? =
17. 17.True or false: on an LED, the leg by the flat edge is the cathode (−). (a) False (b) True
18. 18.🧩 A capacitor in a circuit can … (a) make light (b) measure heat (c) spin a wheel (d) store charge briefly
19. 19.🌈 In the resistor colour code, which number does violet stand for?
20. 20.🌈 Which band is read first on a resistor? (a) the one nearest an end (b) any band (c) the gold band (d) the widest gap
21. 21.🧩 Which component has coloured bands? (a) buzzer (b) resistor (c) diode (d) motor
22. 22.🌈 A resistor has the colour bands yellow, yellow, yellow. What is its value in kilo-ohms (kΩ)? =
23. 23.🌈 A resistor has the colour bands green, black, red. What is its value (in ohms)?
24. 24.🔺 A current of 2 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
25. 25.⚡ A home appliance on the 230 V mains takes 1.5 A. What is its power (in watts)?
26. 26.🧮 A 3 V battery is joined to 2 Ω and 10 Ω resistors in series. What current flows (in amperes)? =
27. 27.🔺 A current of 50 mA flows when 15 V is joined across a resistor. What is its resistance (in ohms)?
28. 28.🧮 Resistors of 33 Ω, 47 Ω and 470 Ω are joined in series. What is the total resistance (in ohms)?
29. 29.🧩 Which component is a resistance knob? (a) resistor (b) transistor (c) capacitor (d) potentiometer
30. 30.📏 Voltmeter or ammeter: which one measures voltage? (a) ammeter (b) voltmeter
31. 31.💡 Does it save or waste electricity to use LED lamps? (a) saves electricity (b) wastes electricity
32. 32.🧾 Which lamp gives the same light for the least power? (a) an oil lamp (b) a candle (c) a filament bulb (d) an LED lamp
33. 33.True or false: the voltmeter is joined in series. (a) True (b) False
34. 34.💡 An LED is joined to a 12 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) may burn out (c) lights up
35. 35.🔺 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
36. 36.🧮 Three equal 30 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
37. 37.💡 Does it save or waste electricity to run fans in empty rooms? (a) saves electricity (b) wastes electricity
38. 38.💡 An LED is joined to a 5 V battery through a 330 Ω resistor; its long leg goes to the − side and its short leg to the + side. What happens? (a) does not light (b) may burn out (c) lights up
39. 39.🧾 One “unit” on an electricity bill is … (a) 1 watt (b) 1 volt (c) 1 ampere (d) 1 kilowatt-hour (kWh)
40. 40.💡 Does it save or waste electricity to iron one shirt at a time? (a) saves electricity (b) wastes electricity

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