How to Calculate Current and Resistance of a Light Bulb

What are the steps to calculate the current and resistance of a light bulb given the power and voltage?

Given Information:

Power = P = 100 Watts

Voltage = V = 220 Volts

Required Information:

a) Current = I = ?

b) Resistance = R = ?

Answer:

a) Current = I = 0.4545 A

b) Resistance = R = 484 Ω

According to the Ohm’s law, the power dissipated in the light bulb is given by

P = VI

Where V is the voltage across the light bulb, I is the current flowing through the light bulb, and P is the power dissipated in the light bulb.

Re-arranging the above equation for current I yields,

I = P/V

I = 100/220

I = 0.4545 A

Therefore, 0.4545 A current is flowing through the light bulb.

According to the Ohm’s law, the voltage across the light bulb is given by

V = IR

Where V is the voltage across the light bulb, I is the current flowing through the light bulb, and R is the resistance of the light bulb.

Re-arranging the above equation for resistance R yields,

R = V/I

R = 220/0.4545

R = 484 Ω

Therefore, the resistance of the bulb is 484 Ω