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Vectorially, the magnetic fields due to both the bar magnets are perpendicular and towards their south poles and their magnitude is B = (mu/4pi) (M/d3) Therefore the resultant magnetic field will be (mu/4pi) (sqrt 2 M/d3) May I know why I'm wrong?

sqrt - square root, mu - permeability constant
Sorry this is already in discussion here, I guess I wrote a new post instead of replying.

Navjyot Kalra , 12 Years ago
Grade 10
anser 1 Answers
Askiitians Tutor Team

It looks like you're diving into the fascinating world of magnetism and vector fields! Let's clarify the situation regarding the magnetic fields produced by bar magnets and how to correctly calculate the resultant magnetic field when considering their orientations and magnitudes.

Understanding Magnetic Fields from Bar Magnets

When dealing with bar magnets, it's essential to recognize how their magnetic fields interact. Each bar magnet generates a magnetic field that can be represented as vectors. The direction of these vectors is crucial, especially when they are oriented at right angles to each other, as you mentioned.

Magnetic Field Magnitude and Direction

The magnetic field \( B \) due to a bar magnet at a distance \( d \) from its center can indeed be expressed as:

  • B = (μ / 4π) (M / d³)

Here, \( M \) represents the magnetic moment of the bar magnet, and \( μ \) is the permeability of the medium. The direction of the magnetic field is always from the north pole to the south pole of the magnet.

Resultant Magnetic Field Calculation

When you have two bar magnets with their magnetic fields oriented perpendicularly towards their south poles, you need to consider how to combine these vector fields. If we denote the magnetic fields from the two magnets as \( B_1 \) and \( B_2 \), both directed towards their respective south poles, the resultant magnetic field \( B_R \) can be calculated using vector addition.

Since the fields are perpendicular, the magnitude of the resultant field can be found using the Pythagorean theorem:

  • B_R = √(B_1² + B_2²)

Substituting the expression for \( B_1 \) and \( B_2 \) gives:

  • B_R = √((μ / 4π) (M / d³))² + ((μ / 4π) (M / d³))²

This simplifies to:

  • B_R = √(2) * (μ / 4π) (M / d³)

Clarifying the Result

Your expression for the resultant magnetic field is correct in terms of the form, but it seems you may have overlooked the vector nature of the fields. The key point is that the resultant field's magnitude is indeed \( (μ / 4π) (√2 M / d³) \), but this is derived from the correct application of vector addition, considering both the magnitude and direction of the fields.

In summary, the resultant magnetic field from two perpendicular bar magnets directed towards their south poles is indeed \( (μ / 4π) (√2 M / d³) \). The important aspect is ensuring that you account for the vector nature of the magnetic fields when they are combined. This approach will help you accurately analyze similar problems in the future!

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