## Tuesday, October 23, 2007

### Study guide H C Verma JEE Physics Ch. 35 MAGNETIC FIELD DUE TO A CURRENT

JEE SYLLABUS

Biot–Savart’s law 35.1 and
Ampere’s law;
Magnetic field near a current-carrying straight wire, along the axis of a circular coil and inside a long straight solenoid;
Force on a moving charge and on a current-carrying wire in a uniform magnetic field.

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Topics covered in H C Verma

35.1 Bio Savart Law
35.2 Magnetic field due to current in a straight wire
35.3 Force between parallel currents
35.4 Field due to a circular current
35.5 Ampere's law
35.6 Magnetic field at a point due to a long straight current
35.7 Solenoid
35.8 Toroid

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Study Plan

Day 1
35.1 Bio Savart Law
35.2 Magnetic field due to current in a straight wire
35.3 Force between parallel currents
WOE 1
Exercises 1,2

Day 2

35.4 Field due to a circular current
35.5 Ampere's law
35.6 Magnetic field at a point due to a long straight current
WOE 2 to 5

Day 3

35.7 Solenoid
35.8 Toroid
Exercises 3 to 10

Day 4
WOE 6 to 10
Exercises 11 to 15

Day 5
WOE 11 to 15
Exercises 16 to 20

Day 6
Exercises 21 to 30

Day 7
Exercises 31 to 40

Day 8
Exercises 41 to 50

Day 9
Exercises 51 to 61

Day 10
Objective I and II
Questions for short answer

Revision Period

Day 11
Concept review

Day 12
Formula review

Days 13 to 20

Test paper problems

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A magnetic field can be represented by lines called the lines of magnetic induction. It also expresses the strength of the mangetic field and it is a vector quantity. In a magentic field, the magnitude of magentic induction is equal to the magnetic flux per unit area at that point.

The unit of magnetic flux is called the weber (symbol Wb). As magnetic induction is equal to the magentic flux per unit area, the SI unit of magnetic induction is weber/metre^2, i.e, Wb/m^2. This unit is also called the tesla (symbol T0

Bio Savart Law

Consider a small element of length dl, of a conductor carrying a current I. Let P be any point at a distance r from the centre of the element along a line making an angle θ with the element. Then, according to this law, the magnetic induction dB at the point P due to the current element dl is given by

dB α I(dl)sinθ/r²

dB = K*I(dl)sinθ/r²

where K is a constant of proportionality whose value depends upon the system of units.

In the SI sytem, K for vacuum or air is written as Mu/4Pi and its value comes out to be 10^(-7) Wb/Am.

Magnetic induction is vector quantity and its direction can be determined by using the right hand rule.