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#field theory

2 public questions tagged with this topic.

Magnetic Field Lines, Bar Magnet and Dipole Moment

The fact that magnetic field lines do not start or end at any point is a direct result of:

**Magnetic dipole moment** quantifies strength and orientation of magnet, m = 2l × q_m where q_m pole strength. Field line concept visualizes B, with closed nature reflecting absence of magnetic monopoles, explaining non-intersection and continuity. Magnetic field lines form closed loops because there are no magnetic monopoles; every field line exiting a region must re-enter, ensuring continuity, as dictated by the absence of isolated magnetic charges in nature. Substituting values gives The absence of magnetic monopoles, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque relation τ = m B sinθ.

Ref: NCERT > Physics Book > Magnetism and Matter > Magnetic Field Lines, Bar Magnet and Dipole Moment

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Coulomb's Law and Force Between Point Charges

What ensures that electric field lines never cross each other in a static field configuration?

**Electrostatic force** described by F = (1/4π ε₀)·q₁q₂/r² obeys Newton's third law. Magnitude depends on q₁q₂ and 1/r², enabling quantitative estimation at given separation, with sign indicating attraction or repulsion. The electric field has a unique direction at each point, defined by the force on a test charge. Crossing lines would imply multiple directions at one point, which is impossible in a static field where the field vector is well-defined. Substituting values gives Unique direction, which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Coulomb's Law and Force Between Point Charges

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