Electrical power of a lightbulb

[Firye Stanly]

Homework Statement

Two identical light bulbs are connected to the ends of the battery. In the first case they are connected in series and in the second they are connected in parallel mode. What is the ratio of the electrical power of light bulbs connected as mentioned?

Homework Equations

$P=I^2R$
$P=\frac{V^2}{R}$

The Attempt at a Solution

Since the voltage is the same and i take a light bulb to be a resistor shouldn't it just be $R_1/R_2$? It somehow should be 1/4 but i don't get how. Total resistance in the first case is $2R$ and in the second is $2/R$ right?

 

[cnh1995]

In the second case, total resistance is not 2/R. What is the formula for equivalent resistance of two parallel resistors?

 

[Firye Stanly]

In the second case, total resistance is not 2/R. What is the formula for equivalent resistance of two parallel resistors?

Parallel resistors $1/R_t = 1/R+1/R$ so its $R/2$ so its $1/4$ oh thanks!