Two identical metal spheres have charges +15μC and +25μC areseparated by a distance. If the spheres are first brought into contact and then separated to the original distance, then the ratio of the new force to the previous force is

### Asked by mohammedmuhsin786786 | 1st Jul, 2021, 08:33: PM

Expert Answer:

### Let q_{1} and q_{2} are the charges on sphere after they are made to get contact with each other.
When they are in contact , both spheres are at same potential.
Since both spheres are identical, and they are at same potential, then q_{1} = q_{2}
Since intial charges on spheres are 15 μC and 25 μC , by conservation of charge , we have
q_{1} + q_{2} = ( 15 + 25 ) μC = 40 μC
Hence , we get , q_{1} = q_{2} = 20 μC .
If the distance between the charges are equal , mutual repulsion force is proportional to the
product of their charge magnitudes.
Hence ratio of new force to previous force = ( 20 × 20 ) / ( 15 × 25 ) = 16/15

_{1}and q

_{2}are the charges on sphere after they are made to get contact with each other.

_{1}= q

_{2}

_{1}+ q

_{2}= ( 15 + 25 ) μC = 40 μC

_{1}= q

_{2}= 20 μC .

### Answered by Thiyagarajan K | 1st Jul, 2021, 09:52: PM

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