Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 309 · 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.🧮 Resistors of 47 Ω, 10 Ω, 22 Ω and 68 Ω are joined in series. What is the total resistance (in ohms)?
2. 2.💡 Does it save or waste electricity to leave fridge door open? (a) wastes electricity (b) saves electricity
3. 3.🌈 A resistor has the colour bands yellow, yellow, red. What is its value (in ohms)?
4. 4.True or false: to use LED lamps saves electricity. (a) True (b) False
5. 5.🧾 Which lamp gives the same light for the least power? (a) an LED lamp (b) a candle (c) a filament bulb (d) an oil lamp
6. 6.Which of these wastes electricity? (a) close the fridge quickly (b) switch off empty rooms (c) set the AC to 24 °C (d) iron one shirt at a time
7. 7.⚡ A device works on 24 V and takes 0.25 A. What is its power (in watts)? =
8. 8.🔺 A current of 0.2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
9. 9.🌈 A resistor has the colour bands brown, white, red. What is its value (in ohms)?
10. 10.True or false: power is measured in ohms (Ω). (a) True (b) False
11. 11.🔺 A current of 0.1 A flows through a 6 Ω resistor. What is the voltage across it (in volts)? =
12. 12.🔺 A current of 0.1 A flows through an 8 Ω resistor. What is the voltage across it (in volts)? =
13. 13.💡 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)?
14. 14.What does a diode do? (a) glows using little power (b) makes a beeping sound (c) lets current go one way (d) boosts a small signal
15. 15.True or false: the voltmeter measures current. (a) False (b) True
16. 16.💡 A red LED uses 2 V and should get 20 mA. It runs from a 5 V supply. What resistor (in ohms) is needed in series?
17. 17.🔺 A current of 1 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
18. 18.📏 Which unit measures voltage? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
19. 19.💡 A red LED uses 2 V and should get 20 mA. It runs from a 6 V supply. What resistor (in ohms) is needed in series?
20. 20.🔺 A current of 0.25 A flows through a 12 Ω resistor. What is the voltage across it (in volts)? =
21. 21.Which of these saves electricity? (a) leave fridge door open (b) close the fridge quickly (c) leave the TV on standby (d) iron one shirt at a time
22. 22.📏 Which unit measures the push of a cell? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
23. 23.📏 Voltmeter or ammeter: which one is joined in series? (a) voltmeter (b) ammeter
24. 24.True or false: the ammeter measures current. (a) True (b) False
25. 25.🔺 A current of 25 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
26. 26.🧮 A 100 Ω resistor is joined in series with two equal 40 Ω resistors that are in parallel with each other. What is the total resistance (in ohms)?
27. 27.⚡ A device works on 5 V and takes 0.2 A. What is its power (in watts)? =
28. 28.💡 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
29. 29.🧮 Two equal 50 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
30. 30.🔺 In the V-I-R triangle, how do we find V? (a) V = I × R (b) V = I ÷ R (c) V = R ÷ I (d) V = I + R
31. 31.⚡ A home appliance on the 230 V mains takes 10 A. What is its power (in watts)?
32. 32.💡 A red LED (it uses 2 V) is joined with a 100 Ω resistor to a 4 V supply. What current flows (in mA)?
33. 33.🌈 A resistor has the colour bands grey, red, orange. What is its value in kilo-ohms (kΩ)? =
34. 34.🧩 Which part changes electrical energy into sound? (a) a diode (b) a buzzer (c) a capacitor (d) a resistor
35. 35.⚡ A 3 W device works on 12 V. What current does it take (in amperes)? =
36. 36.💡 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) may burn out (b) lights up (c) does not light
37. 37.True or false: on an LED, the round-side leg is the cathode (−). (a) True (b) False
38. 38.💡 On an LED, is the longer leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
39. 39.What does a capacitor do? (a) limits the current (b) blows if current is high (c) stores a little charge (d) senses how bright it is
40. 40.🌈 A resistor has the colour bands green, yellow, brown. What is its value (in ohms)?

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