Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 691 · 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 60 W filament bulb is swapped for a 9 W LED lamp that gives about the same light. Both would run for 3 hours. How many watt-hours (Wh) are saved?
2. 2.🔺 A current of 25 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
3. 3.💡 Why does an LED need a resistor in series? (a) to change its colour (b) to make it brighter (c) to store charge (d) to limit the current
4. 4.📏 How many amperes (A) is 2250 mA? =
5. 5.💡 Does it save or waste electricity to use LED lamps? (a) wastes electricity (b) saves electricity
6. 6.⚡ A home appliance on the 230 V mains takes 2 A. What is its power (in watts)?
7. 7.True or false: the voltmeter measures current. (a) False (b) True
8. 8.💡 On an LED, is the shorter leg the anode (+) or the cathode (−)? (a) anode (+) (b) cathode (−)
9. 9.🧩 A capacitor in a circuit can … (a) spin a wheel (b) store charge briefly (c) make light (d) measure heat
10. 10.🧮 A 1.3 V battery is joined to 5 Ω and 8 Ω resistors in series. What current flows (in amperes)? =
11. 11.🧩 Which part changes electrical energy into sound? (a) a resistor (b) a diode (c) a buzzer (d) a capacitor
12. 12.🔺 A current of 20 mA flows through a 250 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🧩 Which part changes electrical energy into movement? (a) a resistor (b) a motor (c) a fuse (d) an LED
14. 14.True or false: energy used each second is measured in watts (W). (a) False (b) True
15. 15.⚡ A 3 W device works on 6 V. What current does it take (in amperes)? =
16. 16.🔺 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
17. 17.🌈 In the resistor colour code, which number does brown stand for?
18. 18.🌈 A resistor has the colour bands blue, yellow, brown. What is its value (in ohms)?
19. 19.🔺 A 2 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
20. 20.🧩 Which component senses how hot it is? (a) potentiometer (b) capacitor (c) thermistor (d) LED
21. 21.📏 Which unit measures how much a part resists? (a) watt (W) (b) volt (V) (c) ampere (A) (d) ohm (Ω)
22. 22.🧮 A 0.9 V battery is joined to 5 Ω and 4 Ω resistors in series. What current flows (in amperes)? =
23. 23.🔺 A current of 20 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
24. 24.True or false: an LDR makes things spin. (a) True (b) False
25. 25.🧮 Two equal 20 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.🧮 Two equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
27. 27.Which of these wastes electricity? (a) unplug idle chargers (b) use daylight to read (c) run fans in empty rooms (d) use LED lamps
28. 28.True or false: on an LED, the longer leg is the anode (+). (a) True (b) False
29. 29.🌈 A resistor has the colour bands violet, grey, black. What is its value (in ohms)?
30. 30.⚡ A device works on 6 V and takes 1.5 A. What is its power (in watts)? =
31. 31.⚡ A home appliance on the 230 V mains takes 4 A. What is its power (in watts)?
32. 32.🧮 Resistors of 470 Ω, 33 Ω, 10 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
33. 33.🔺 A current of 40 mA flows when 4.8 V is joined across a resistor. What is its resistance (in ohms)?
34. 34.📏 Which unit measures current? (a) ampere (A) (b) volt (V) (c) watt (W) (d) ohm (Ω)
35. 35.💡 What happens if an LED is put in backwards? (a) it lights brighter (b) it changes colour (c) it makes a sound (d) it does not light
36. 36.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets bigger (b) stays the same (c) becomes zero (d) gets smaller
37. 37.🧮 Resistors of 22 Ω and 10 Ω are joined in series. What is the total resistance (in ohms)?
38. 38.🔺 A 1 V supply is joined across a 10 Ω resistor. What current flows (in amperes)? =
39. 39.⚡ A 0.6 W device works on 6 V. What current does it take (in amperes)? =
40. 40.🌈 A resistor has the colour bands brown, yellow, yellow. What is its value in kilo-ohms (kΩ)? =

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