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 (1)/(R)=(1)/(R_1)=+(1)/(R_2)`

`\\ \sf\longmapsto (1)/(R)=(1)/(2)+(1)/(2)`

`\\ \sf\longmapsto (1)/(R)=1`

`\\ \sf\longmapsto R=1\Omega`

Now

Using ohms law

`\boxed{\sf (V)/(I)=R}`

`\\ \sf\longmapsto I=(V)/(R)`

In series:-

`\\ \sf\longmapsto I=(8)/(4)`

`\\ \sf\longmapsto I=2A`

In parallel

`\\ \sf\longmapsto I=(8)/(1)`

`\\ \sf\longmapsto I=8A`