Video Lecture
Theory For Notes Making
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Objective Assignment
Q.1
If a long cylindrical conductor carries a steady current parallel to its length,
(a) the electric field along the axis is zero
(b) the magnetic field along the axis is zero
(c) the magnetic field outside the conductor is zero
(d) the direction of electric field outside the conductor is perpendicular to the length of conductor .
Ans. (b)
Q.2
A vertical solenoid has 200 turns in a length of 0.40 m and carries a current of 3 A in the direction shown. The flux density in the middle in tesla (T) is about
(a) 1.9 ´ 10-3 and downward
(b) 2.9 ´ 10-5 and upward
(c) 1.9 ´ 10-3 and upward
(d) 0.19 and upward
Ans :(C)
Q.3
A uniformly distributed current I flows through a cylindrical conductor of radius r. The magnetic field at a point x (< r) is
(a) \frac{{{{\mu }_{0}}I}}{{2\pi x}}
(b) \frac{{{{\mu }_{0}}I}}{{2\pi (x-r)}}
(c) \frac{{{{\mu }_{0}}Ix}}{{2\pi {{r}^{2}}}}
(d) \frac{{{{\mu }_{0}}I}}{{2\pi {{{(x-r)}}^{2}}}}
Ans. (c)
4.
A current I flows uniformly along a solid rod of radius R. Show that the B–field inside this rod, at a distance r from the axis is,
(a) B=\frac{{{{\mu }_{1}}Ir}}{{3\pi {{R}^{2}}}}
(b) B=\frac{{{{\mu }_{0}}Ir}}{{5\pi {{R}^{3}}}}
(c) B=\frac{{{{\mu }_{0}}Ir}}{{9\pi {{R}^{4}}}}
(d) B=\frac{{{{\mu }_{0}}Ir}}{{2\pi {{R}^{2}}}}
Ans (d)
Subjective Assignment
Q.1
The magnetic field at the axis of a long solenoid is `B’. What is the magnetic field near the ends of it ?
Q.2.
A current is set up in a long copper pipe. Is there a magnetic field (i) inside (ii)outside the pipe’?
Q.3
Trace the magnetic field lines for the following cases
(a) straight current carrying conductor
(b) current carying solenoid
(c) current carrying toroidal
(d) curent carrying circular loop.
Q.4
Give a magnetic field configuration which has no definite north or south pole.
Q.5
What is the magnetic field outside an ideal solenoid ?
Q.6
What is the force acting on a 0.04m long wire placed inside a solenoid near its center on the axis at an angle of 60o with its axis ? The wire carries a current of 10A and the magnetic field due to the solenoid is 0.225T.
Q.7
A toroid has a core of inner radius 25cm and outer radius 26cm, around which 3500 turns of a wire are wound .If the current in the wire is 10A , what is the magnetic field
(a) outside the toroid (b) inside the toroid
(c) in the empty space surrounded by the toroid.
Q.8
A circular loop of radius 10cm and cureent 20amp is suspended freely inside a solenoid of radius 30cm and have 4000turns in a length of 30cm. and carrying a current of 5amp. Find the torque acting on the loop if
(a) its plane is making 30 with the axis of the solenoid
(b) the axis of the loop is making 90 with the axis of the solenoid
(c) the plane of the loop is parallel to the axis of the solenoid
(d) the plane of the loop is perpendicular to the axis of the solenoid.
Q.9
A wire of length 1cm is placed inside a solenoid having three layers winding each of 1000turns.If the length of the solenoid is 30cm and the wire is carrying a current of 2amp then find the current passing through the solenoid so that the net weight of the wire remain zero inside the solenoid.Given the mass of the wire as 10gm and is placed perpendicular to axis of the solenoid in horizontal plane.
Q.10
Draw a diagram to show the pattren of magnetic field of
(a) solenoid (b)toroidal.
Q.11
A solenoid is to be designed to produce a magnetic field of 0.1 T at its center. The radius is to be 5 cm and the length 50, and the available wire can carry a maximum current of 10 A
(A) How many turns per unit length should the solenoid have?
(B) what total length of wire is required?
Q.12
If the current sensitivity of a moving coil galvanometer is increased by 20%, its resistance also increase by 1.5 times. How will the voltage sensitivity of galvanometer be affected ‘?