Question

A light bulb for use with the 220 V mains is rated at 100 W.

(a) What current will flow through the bulb?
(b) If the bulb converts 20% of the energy to light, how much light energy is produced per second?

Answer 1

So, 20W of light energy is produced per second.

Step-by-step explanation:

a) To calculate the current flowing through the bulb, we use the formula:

I = P / V

Where P is the power in watts (100 W) and V is the voltage (220 V).

I = 100 / 220 = 0.45 A

b) To find the light energy produced per second, we use the formula:

E = P x t

Where P is the power in watts (100 W) and t is the time in seconds.

As we know only the power and not the time, we have to calculate the energy efficiency of the bulb.

Efficiency = (Energy output/ Energy input) * 100

Efficiency = (Light energy output / Total energy input) * 100

Let's assume that the bulb is on for 1 sec

Efficiency = (Light energy output / 100W) * 100

Light energy output = (Efficiency / 100) * 100W = 20W

Efficiency = 20%

So, 20W of light energy is produced per second.

Answer 2

So, 20W of light energy is produced per second.

Step-by-step explanation:

a) To calculate the current flowing through the bulb, we use the formula:

I = P / V

Where P is the power in watts (100 W) and V is the voltage (220 V).

I = 100 / 220 = 0.45 A

b) To find the light energy produced per second, we use the formula:

E = P x t

Where P is the power in watts (100 W) and t is the time in seconds.

As we know only the power and not the time, we have to calculate the energy efficiency of the bulb.

Efficiency = (Energy output/ Energy input) * 100

Efficiency = (Light energy output / Total energy input) * 100

Let's assume that the bulb is on for 1 sec

Efficiency = (Light energy output / 100W) * 100

Light energy output = (Efficiency / 100) * 100W = 20W

Efficiency = 20%

So, 20W of light energy is produced per second.