Question

A 250V lamp has a total flux of 1500
lumens and takes a current of 0.4A.
Lumen per watt is.......lumen/W *
10​

Answer 1

Given:

A 250V lamp has a total flux of 1500 lumens and takes a current of 0.4A.

To find:

Value of Lumens/watt ?

Calculation:

First of all, let's find out the power delivered by the lamp :

• Power can be calculated as the product of potential difference and the the current flowing through the circuit.

$\therefore \: P = voltage \times current$

$\implies\: P = 250 \times 0.4$

$\implies\: P = 100 \: watt$

Now, value of Lumens/watt:

$\therefore \: L/W = \dfrac{1500}{100}$

$\implies \: L/W = 15$

So, flux per unit power is 15 Lumen/watt.