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An unknown resistance is connected in pa...

An unknown resistance is connected in parallel with a `15Omega` resistance and a 12 V battery. What is the value of the unknown resistance if the current in the circuit is 2A?

A

`10 Omega`

B

`20 Omega`

C

`30 Omega`

D

`40 Omega`

Text Solution

Verified by Experts

The correct Answer is:
A
`(1)/(R_(p))=(1)/(15)+(1)/(R) rArr (R+15)/(15R)`
`R_(p)=(15R)/(15+R)`
`V=IR_(p)`
`12= 2xx(15R)/(15+R)=(30R)/(15+R)`
`12(15+R)=30 R`
`180+12R=30R`
`180=30R-12R`
`180=18R`
`R=10 Omega`
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