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A very long cylindrical wire is carrying a current Io distributed uniformly over its cross-section area. O is the centre of the cross-section of the wire and the direction of current is into the plane of the figure. The value of ABB·dl along the path AB (from A to B) is

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Important Questions on Magnetic Effect of Current

MEDIUM
A toroid with thick windings of N turns has inner and outer radii R1 and R2 respectively. If it carries certain steady current I, the variation of the magnetic field due to the toroid with radial distance is correctly graphed in
MEDIUM
A long straight wire of radius a carries a steady current I . the current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B' , at radial distances a2 and 2a respectively, from the axis of the wire is:
HARD

Figure A and B shown two long straight wires of circular cross-section ( a and b with a<b ), carrying current I which is uniformly distributed across the cross-section. The magnitude of magnetic field B varies with radius r and can be represented as:

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MEDIUM
In a co-axial, straight cable, the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero
MEDIUM

A current I is flowing along an infinite, straight wire, in the positive Z- direction and the same current is flowing along a similar parallel wire 5 m apart, in the negative Z- direction. A point P is at a perpendicular distance 3 m from the first wire and 4 m from the second. What will be the magnitude of the magnetic field B of P?

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A long thin hollow metallic cylinder of radius R has a current i ampere. The magnetic induction B away from the axis at a distance 'r' from the axis varies as shown in

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EASY

A very long straight wire of radius r carries current I. Intensity of magnetic field B at a point lying at a perpendicular distance a from the axis is  _____ (where a<r).

EASY
The magnitude of the magnetic field inside a solenoid of length, 300 cm and made up of 450 turns is 9×10-3 T. The current carried by the solenoid is (assume the radius of solenoid << 300 cm )
EASY
Two parallel conducting wires of equal lengths placed distance d apart carry currents I1 and I2 respectively in opposite directions. The resultant magnetic field at the midpoint of both the wires is (μo= permeability of free space.)
MEDIUM

Two very long straight wires are set parallel to each other. Each carries a current I in the same direction and the separation between them is 2r. The intensity of the magnetic field at point P as shown in the figure is _________.

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MEDIUM
A coaxial cable consists of an inner wire of radius a surrounded by an outer shell of inner and outer radii b and c respectively. The inner wire carries an electric current i0 which is distributed uniformly across cross-sectional area. The outer shell carries an equal current in opposite direction and distributed uniformly. What will be the ratio of the magnetic field at a distance x from the axis when i x<a and ii a<x<b ?
MEDIUM
A steady current I flows down a long rod of radius ain such a way that its current density J=kr2r^, where k is a positive constant of appropriate dimensions, r is the radial distance from the axis and  r^ is the unit vector along the radial direction. Then the magnitude of the magnetic field at any point  rr<a inside the rod is
EASY
The magnetic field intensity (H) at the centre of a long solenoid carrying a current of 2 A, is found to be 1000 A. The number of turns per centimeter of the solenoid is
( Use μ0=4π×10-7 T m A-1)
MEDIUM
 A thick current carrying cable of radius R carries current I uniformly distributed across its cross-section. The variation of magnetic field B(r) due to the cable with the distance r from the axis of the cable is represented by:
EASY
If the number of turns per unit length of a solenoid is doubled, what happens to the magnetic field in the solenoid?
HARD

A circuit is in the form of a regular hexagon of side a with its centre at the point O. A current I flows in the circuit.

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The magnitude of the magnetic field at O is

EASY
A long hollow cylindrical metal tube has an inner radius R and outer radius 2R . A current I flows along the length of the tube and is uniformly distributed along the cross section of the tube. The length of the tube is much greater than 2R. If r denotes the distance from the axis of the cylinder, then the magnitude of the magnetic field in the hollow part of the tube (0<r<R) is approximately
EASY
The magnetic field due to a straight long conductor of uniform cross-section of radius a and carrying a steady current is represented by
MEDIUM
A uniform current is flowing along the length of an infinite, straight, thin, hollow cylinder of radius R. The magnetic field B produced at a perpendicular distance d from the axis of the cylinder is plotted in a graph. Which of the following figures looks like the plot?
MEDIUM
A long cylindrical wire of radius R carries a uniform current I flowing through it. The variation of magnetic field with distance 'r' from the axis of the wire is shown by