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22 September, 06:57

The power rating of a light bulb (such as a 100-W bulb) is the power it dissipates when connected across a 120-V potential difference. Part A What is the resistance of a 100 W bulb?

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  1. 22 September, 07:18
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    Complete Question:

    The power rating of a light bulb (such as a 100-W bulb) is the power it dissipates when connected across a 120-V potential difference.

    Part A: What is the resistance of a 100 W bulb?

    part B: Current flowing through a 100 W bulb?

    part C: Find the resistance of a 40 W bulb

    part D: Current flowing through a 40W bulb

    Answer:

    a) Resistance of a 100 W bulb, R = 144 ohms

    b) Current flowing through a 100 W bulb, I = 0.833 A

    c) Resistance of a 40W bulb, R = 360 ohms

    d) current in a 40W bulb, I = 0.33 A

    Explanation:

    a) Resistance of the 100 W bulb

    Power, P = 100 W

    Potential difference, V = 120 V

    P = V²/R

    R = V²/P

    R = 120²/100

    R = 144 ohms

    b) the current flowing through the bulb

    According to Ohm's law, V = IR

    I = V/R

    I = 120/144

    I = 0.833 A

    c) Find the resistance of a 40 W bulb

    Since the voltage supplied is constant, P = V²/R

    P = 40 W

    V = 120 V

    40 = 120²/R

    R = 120²/40

    R = 360 ohms

    d) current flowing through the 40 W bulb

    V = IR

    I = V/R

    I = 120/360

    I = 0.33 A
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