Practical No. 07: Determination of neutral points by magnetic compass.
XIII. Interpretation of Results
- The neutral points were successfully located on the equatorial line when the North pole of the magnet faced geographic North, and on the axial line when the South pole faced geographic North.
XIV. Conclusions and Recommendations
- It is concluded that neutral points exist where the magnetic field due to the magnet exactly cancels the Earth’s horizontal magnetic field.
- It is recommended to use a large sheet of paper and mark points carefully for accurate plotting of field lines.
XV. Practical Related Questions & Answers
Q1. Write reason for deflection in compass needle, when brought near bar magnet.
- Answer: The compass needle deflects because it experiences a torque due to the magnetic field of the bar magnet, which is much stronger than the Earth’s magnetic field at that specific point.
Q2. Give the number of neutral points obtained if we place a bar magnet in east west direction.
- Answer: Two neutral points are obtained for any orientation of the bar magnet.
Q3. Write material and length of given bar magnet.
- Answer: The bar magnet is made of steel and its length is 5 cm (Note: You can write the exact length of the magnet used in your college lab, e.g., 5 cm or 7 cm).
Q4. Give the position of the neutral point, when a bar magnet is placed with its South Pole pointing towards geographic north.
- Answer: When the South Pole points to geographic north, the neutral points lie on the axial line of the bar magnet.
Q5. Write the neutral point formula?
- Answer: At a neutral point, the magnetic field due to the magnet (B) is equal to the Earth’s horizontal magnetic field (B_H).
- For a point on the axial line: B = (μ₀ / 4π) × (2M / d³) = B_H
- For a point on the equatorial line: B = (μ₀ / 4π) × (M / d³) = B_H
(where M is the magnetic moment and d is the distance from the center).
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