Two long conductors, separated by a distance d carry current I₁ and I₂ in the same direction. They exert a force F on each other. Now the current in one of them increased to two times and its direction reversed. The distance is also increased to 3d. The new value of the force between them is

−2F

F/3

−2F/3

-F/3

Solution

−2F/3

Force acting between two current carrying conductors
$straight F space equals space fraction numerator straight mu subscript 0 over denominator 2 straight pi end fraction fraction numerator straight I subscript 1 straight I subscript 2 over denominator straight d end fraction straight I space....... space left parenthesis straight i right parenthesis$
where d = distance between the conductors,
l = length of each conductor
$straight F apostrophe space equals space fraction numerator straight mu subscript 0 over denominator 2 straight pi end fraction space fraction numerator left parenthesis negative 2 straight I subscript 1 right parenthesis left parenthesis straight I subscript 2 right parenthesis over denominator left parenthesis 3 straight d right parenthesis end fraction. space straight I space equals space minus space fraction numerator straight mu subscript 0 over denominator 2 straight pi end fraction space fraction numerator left parenthesis negative 2 straight I subscript 1 right parenthesis left parenthesis straight I subscript 2 right parenthesis over denominator left parenthesis 3 straight d right parenthesis end fraction. straight I space equals space minus space fraction numerator straight mu subscript 0 over denominator 2 straight pi end fraction fraction numerator 2 straight I subscript 1 straight I subscript 2 over denominator 3 straight d end fraction. space straight I space..... space left parenthesis ii right parenthesis space thus comma space from space equations space left parenthesis straight i right parenthesis space and space left parenthesis ii right parenthesis space fraction numerator straight F apostrophe over denominator straight F end fraction space equals space minus space 2 over 3 straight F apostrophe space equals space minus 2 straight F divided by 3$

Some More Questions From Magnetism and Matter Chapter

Answer the following question:
The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

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The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

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The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer the following question:
The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?

Answer the following question:
The earth’s field departs from its dipole shape substantially at large distances (greater than about 30,000 km). What agencies may be responsible for this distortion?

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Magnetism And Matter

Some More Questions From Magnetism and Matter Chapter

Answer the following question:
The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

Answer the following question:
The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

Answer the following question:
The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer the following question:
The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?

Answer the following question:
The earth’s field departs from its dipole shape substantially at large distances (greater than about 30,000 km). What agencies may be responsible for this distortion?

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For Daily Free Study Material Join wiredfaculty

Magnetism And Matter

Some More Questions From Magnetism and Matter Chapter

Answer the following question:The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

Answer the following question:The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

Answer the following question:The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer the following question:The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?

Answer the following question:The earth’s field departs from its dipole shape substantially at large distances (greater than about 30,000 km). What agencies may be responsible for this distortion?

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Answer the following question:
The earth's magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?

Answer the following question:
The earth's core is known to contain iron. Yet geologists do not regard this as a source of the earth's magnetism. Why?

Answer the following question:
The charged currents in the outer conducting regions of the earth's core are thought to be responsible for earth's magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Answer the following question:
The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth's field in such distant past?

Answer the following question:
The earth’s field departs from its dipole shape substantially at large distances (greater than about 30,000 km). What agencies may be responsible for this distortion?