# A positively charged rod X is brought near an uncharged metal sphere Y

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## A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that Y has

A. no charge and a zero potential.

B. a positive charge and a zero potential.

C. a negative charge and a positive potential.

D. a negative charge and a negative potential.

C

## EXPLANATION…

• Sphere Y was initially neutral.
• When positively charged rod, X is brought near it, negative charges will be induced on Y because unlike charges attract each other.
• Also, because like charges repel each other, positive charges will be repelled by rod X.
• Touching the sphere with a finger while keeping X close will conduct the repelled positive charges out of the sphere into probably the earth.
• And the remaining negative charges will leave Y a negatively charged sphere.

Please also note that the potential will be positive and not negative because electric potential is a scalar quantity and not a vector quantity, and so a negative sign does not matter.

### Now for the right answer to the above question:

1. Option A is incorrect. there will be negative charges left.
2. Option B is incorrect. the charges left will be negative.
3. C is correct. yes, there will be left over negative charges, and because electric potential is a scalar quantity, the potential will be positive irrespective of the sign of the charge.
4. D is not the correct answer. No, the potential will be positive and not negative.

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• Electric potential is a scalar quantity.
• Please remember that scalar quantities only have positive magnitudes and no direction; therefore, negativity in sign makes no difference as far as scalars are concerned.

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/ culled from 2018 JAMB-UTME physics question 29 /