Question

Two identical light bulbs, each with resistance R = 2  are connected to a source with E = 8 V and negligible internal resistance. Find the current through each bulb, if the bulb in series and (ii) in parallel. ​

Answer 1

• R_1=R_2=2ohm
• V=8V

In series

$\boxed{\sf R=R_1+R_2}$

$\\ \sf\longmapsto R=2+2$

$\\ \sf\longmapsto R=4\Omega$

In parallel

$\\ \sf\longmapsto \dfrac{1}{R}=\dfrac{1}{R_1}=+\dfrac{1}{R_2}$

$\\ \sf\longmapsto \dfrac{1}{R}=\dfrac{1}{2}+\dfrac{1}{2}$

$\\ \sf\longmapsto \dfrac{1}{R}=1$

$\\ \sf\longmapsto R=1\Omega$

Now

Using ohms law

$\boxed{\sf \dfrac{V}{I}=R}$

$\\ \sf\longmapsto I=\dfrac{V}{R}$

In series:-

$\\ \sf\longmapsto I=\dfrac{8}{4}$

$\\ \sf\longmapsto I=2A$

In parallel

$\\ \sf\longmapsto I=\dfrac{8}{1}$

$\\ \sf\longmapsto I=8A$