Question:
The magnetic induction at a point P which is at the distance of 4 cm from a long current carrying wire is $ 10^{-3}$ T. The field of induction at a distance 12 cm from the current will be
The magnetic induction at a point P which is at the distance of 4 cm from a long current carrying wire is $ 10^{-3}$ T. The field of induction at a distance 12 cm from the current will be
Updated On: May 25, 2026
- $3.33 \times {10}^{-4} \,T $
- $1.11 \times {10}^{-4} \,T $
- $33 \times {10}^{-3}\, T $
- $ 9 \times {10}^{-3}\, T $
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The Correct Option is A
Solution and Explanation
$B \propto 1/r . $ By Ampere's law.
As the distance is increased to three times, the
magnetic induction reduces to one third.
Hence $B =\frac{1}{3}\times {10}^{-3}$ tesla $=3.33 \times{10}^{-4}$ tesla
As the distance is increased to three times, the
magnetic induction reduces to one third.
Hence $B =\frac{1}{3}\times {10}^{-3}$ tesla $=3.33 \times{10}^{-4}$ tesla
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Concepts Used:
Magnetic Field
The magnetic field is a field created by moving electric charges. It is a force field that exerts a force on materials such as iron when they are placed in its vicinity. Magnetic fields do not require a medium to propagate; they can even propagate in a vacuum. Magnetic field also referred to as a vector field, describes the magnetic influence on moving electric charges, magnetic materials, and electric currents.
A magnetic field can be presented in two ways.
- Magnetic Field Vector: The magnetic field is described mathematically as a vector field. This vector field can be plotted directly as a set of many vectors drawn on a grid. Each vector points in the direction that a compass would point and has length dependent on the strength of the magnetic force.
- Magnetic Field Lines: An alternative way to represent the information contained within a vector field is with the use of field lines. Here we dispense with the grid pattern and connect the vectors with smooth lines.
Properties of Magnetic Field Lines
- Magnetic field lines never cross each other
- The density of the field lines indicates the strength of the field
- Magnetic field lines always make closed-loops
- Magnetic field lines always emerge or start from the north pole and terminate at the south pole.