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?

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