If two conducting spheres are separately charged and then brought in contact

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Q: 70 (CDS-I/2013)
If two conducting spheres are separately charged and then brought in contact—

question_subject: 

Science

question_exam: 

CDS-I

stats: 

0,13,25,11,13,9,5

keywords: 

{'final potential': [0, 0, 1, 1], 'original potential': [0, 0, 1, 1], 'total charge': [0, 0, 0, 1], 'total energy': [0, 0, 1, 4], 'spheres': [0, 0, 1, 2]}

When two conducting spheres with separate charges are brought in contact, the charges will redistribute among the two spheres to achieve electrical equilibrium. This means that the total charge on the two spheres will be conserved, as stated in option 2.

Option 1 is incorrect because the total energy of the two spheres is not conserved. When the spheres are brought in contact, some energy is lost as heat due to the resistance in the conductors.

Option 3 is also incorrect because although the total charge is conserved, the total energy is not conserved.

Option 4 is incorrect because the final potential of the two spheres after contact does not necessarily become the mean of the original potentials. The charges on the spheres and their respective conductivities determine the final potential. If the spheres have different charges and conductivities, the final potential will not be the mean.

Therefore, the correct answer is option 2: the total charge on the two spheres is conserved.