**Correct Option: A. The negative charges in the sphere move away from the rod, leaving the side closest to the rod positively charged.** ### Detailed Explanation: When a negatively charged rod is brought near a neutral metal sphere, the distribution of charges within the sphere changes due to a phenomenon known as **electrostatic induction**. Here’s a step-by-step breakdown of what happens: 1. **Understanding Charge Distribution**: - A neutral metal sphere has an equal number of positive and negative charges (protons and electrons). In a neutral state, these charges are uniformly distributed throughout the sphere. 2. **Introducing the Negatively Charged Rod**: - When the negatively charged rod approaches the sphere, the electric field created by the rod exerts a force on the charges within the sphere. 3. **Movement of Charges**: - The negatively charged electrons in the sphere are repelled by the negatively charged rod. This repulsion causes the electrons to move away from the side of the sphere that is closest to the rod. - As the electrons move away, the side of the sphere closest to the rod becomes positively charged because there are now more protons (positive charges) than electrons (negative charges) in that region. 4. **Resulting Charge Distribution**: - The side of the sphere nearest to the rod becomes positively charged, while the side farthest from the rod retains the excess negative charge (since the electrons have moved away). This creates a separation of charge within the sphere, known as polarization. 5. **Induced Charge**: - The sphere as a whole remains neutral because the total number of positive and negative charges has not changed; they have merely been redistributed. However, the induced positive charge on the side closest to the rod can attract the rod, demonstrating the effect of electrostatic induction. ### Why Other Options Are Incorrect: - **Option B**: "The positive charges in the sphere move away from the rod, leaving the side closest to the rod negatively charged." - This option is incorrect because it suggests that positive charges (protons) can move. In a solid conductor, only the electrons (negative charges) are free to move. Protons are fixed in place within the atomic structure and cannot move to create a charge separation. - **Option C**: "The charges in the sphere remain uniformly distributed, as they are unaffected by external charges." - This option is incorrect because it ignores the principle of electrostatic induction. External charges, such as the negatively charged rod, do affect the distribution of charges within a conductor. The presence of the rod causes the charges in the sphere to redistribute. - **Option D**: "The sphere becomes positively charged as a whole due to the influence of the rod." - This option is misleading. While the side of the sphere closest to the rod becomes positively charged, the sphere itself does not gain a net positive charge. The overall charge of the sphere remains neutral; it is only the distribution of charges that changes. ### Summary of Key Points: - A negatively charged rod induces a charge separation in a neutral metal sphere. - Electrons in the sphere are repelled by the rod, moving away from it and leaving the side closest to the rod positively charged. - The sphere remains neutral overall, but the charge distribution becomes polarized. - Only negative charges (electrons) can move in a conductor, while positive charges (protons) remain fixed. This understanding of charge distribution and electrostatic induction is crucial for grasping concepts in electrostatics and the behavior of conductors in electric fields.