A copper ring is moved towards the north pole of a bar magnet. Then

Options

A. the ring will not be affected
B. the ring will tend to get warm
C. an alternating current will flow in the ring
D. the ring will be positively charged

Answer

**Step-by-Step Solution:**

1. **Understanding the Setup**: We have a copper ring and a bar magnet with a defined north and south pole. The copper ring is being moved towards the north pole of the magnet.

2. **Induction of Current**: According to Faraday's law of electromagnetic induction, when a conductor (like a copper ring) moves through a magnetic field, an electromotive force (emf) is induced in the conductor. This means that as the copper ring approaches the north pole of the magnet, an emf will be generated in the ring.

3. **Current Flow**: The induced emf causes a current to flow through the copper ring. Since copper is a good conductor, the current will flow easily.

4. **Heat Production**: According to Joule's law of heating, when current flows through a conductor, heat is produced. The amount of heat generated can be calculated using the formula \( H = I^2 R T \), where \( H \) is the heat produced, \( I \) is the current, \( R \) is the resistance of the ring, and \( T \) is the time for which the current flows.

5. **Temperature Increase**: As heat is produced in the copper ring due to the flowing current, the temperature of the ring will increase.

6. **Evaluating the Statements**:
- The first statement claims that the ring will not be affected. This is incorrect because the ring gets warm due to heat production.
- The second statement claims that the ring will tend to get warm. This is correct as heat is generated.
- The third statement claims that an alternating current will flow in the ring. This is incorrect because the current induced is direct, not alternating.
- The fourth statement claims that the ring will be positively charged. This is incorrect as there is no transfer of charge that would lead to a net positive charge.

7. **Conclusion**: The only correct statement is that the ring will tend to get warm.

**Final Answer**: The correct statement is: "The ring will tend to get warm."

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