Q1. State Ampere's circuital law ?
Ans: It states that the line integral of magnetic field ⃗(B) around any closed path or circuit is equal to μ0 (absolute permeability of free space) times the total current (I) threading the closed circuit.
Mathematically, ∫ ⃗B × ⃗dI = μ0 I
Q2. Write an expression for the magnetic field produced by an infinitely long straight wire carrying a current I, at a short perpendicular distance a from itself.
Ans: It is given by
B = μ 0 / 4 π × 2 I/a
Q3. What kind of magnetic field is produced by an infinitely long current carrying conductor?
Ans: Magnetic field lines are concentric circular loops in a plane perpendicular to the straight conductor. The centres of the circular magnetic field lines lie on the conductor.
Q4. What kind of magnetic field is produced due to straight solenoid?
Ans: The magnetic field produced by a straight solenoid is similar to that produced by a bar magnet.
Q5. What is toroid ?
Ans: An anchor ring, around which a large number of turns of a metallic wire are wound, is called a toroid.
Q6. Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. why?
Ans: The magnetic field lines always form closed loops. As the turns of the wires in a toriodal solenoid are wound over its core in circular form, the field lines are confined within the core of the toroid.
In a straight solenoid, the magnetic field lines can not form closed loops within the solenoid.
Q7. What is a solenoid ? Give the magnitude of magnetic field developed at a pint well inside a solenoid carrying current.
Ans: A solenoid is a circular coil of a large number of turns, such that the turns of the solenoid run parallel to its length.
The magnetic field at a point well inside the solenoid,
B = μ0 n I
Here, n is number of turns per unit length of the solenoid.
Q8.Write down an expression for the flux density B inside a long straight solenoid, explaining the symbols use.
How much is the flux density B at the centre of a long solenoid?
Ans: The magnetic field due to a long straight solenoid at a point well inside it, is given by
B = μ0 n I
Here, μ0 is the permeability of free space, n is the number of turns per unit length of the solenoid and I is the current flowing through it.
Q9. Give two similarities between Biot Savart's law for magnetic fields and Coulomb's law for electrostatic fields ?
Ans: (i)Both the laws apply to the fields, which obey inverse square law.
(ii) Both the laws apply to the fields, which obey superposition principle.
Q10. In what respect does a wire carrying a current differ from a wire, which carries no current ?
Ans: A current carrying wire produces magnetic field. It is because, when current flows throught a wire, electrons move inside it along a definite direction. On the other hand, in a wire which carries no current, electrons are in motion in random direction. Such a wire does not produce any magnetic field.
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