Interstellar space has an extremely weak magnetic field of the order of `10^(-12)T.` Can such a weak fleld be of any significant consequence? Explain.

A 800 turn coil of effective area 0.05 m^2 is kept perpendicular to a magnetic field 5 xx 10^(-5) T. When the plane of the coil is rotated by 90^@ around any of its coplanar axis in 0.1 s, the emf induced in the coil will be

A square loop of side 12 cm with its sides parallel to X and Y axes is moved with a velocity of 8 "cm s"^(-1) in the positive x-direction in an environment containing a magnetic field in the positive z-direction. The field is neither uniform in space nor constant in time. It has a gradient of 10^(-3) "T cm"^(-1) along the negative x-direction (that is it increases by 10^(-3) "T cm"^(-1) as one moves in the negative x-direction), and it is decreasing in time at the rate of 10^(-3) T s^(-1) . Determine the direction and magnitude of the induced current in the loop if its resistance is 4.50 mOmega .

A 100 turn closely wound circular coil of radius 10 cm carries a current of 3.2 A. (a) What is the field at the centre of the coil? (b) What is the magnetic moment of this coil? The coil is placed in a vertical plane and is free to rotate about a horizontal axis which coincides with its diameter. A uniform magnetic field of 2T in the horizontal direction exists such that initially the axis of the coil is in the direction of the field. The coil rotates through an angle of 90^@ under the influence of the magnetic field. (c) What are the magnitudes of the torques on the coil in the initial and final position? (d) What is the angular speed acquired by the coil when it has rotated by 90^@ ? The moment of inertia of the coil is 0.1 kg m^2 .

A magnetic needle is hung by an untwisted wire, so that it can rotate freely in the magnetic meridian. In order to keep it in the horizontal position, a weight of 0.1 g is kept or one end of the needle. If the magnetic pole strength of this needle is 10 Am, find the value of the vertical component of the earth's magnetic field. (g= 9.8 ms^(-2) )

A jet plane is travelling towards west at a speed of 1800 km/h. What is the voltage difference developed between the ends of the wing having a span of 25 m, if the Earth's magnetic field at the location has a magnitude of 5 xx 10^(-4) T and the dip angle is 30^@ .

The neutron is a particle with zero charge still it has a non-zero magnetic moment with z-component 9.66 xx 10^(-27) A-m^(2) . This can be explained by the internal structure of the neutron. The evidence indicates that a neutron is composed of three fundamental particles calleed quarks : an "up" (u) quark, of charge + (2e)/(3) , and two "down" (d) quarks, each of change - (e)/(3) . The combinations of the three quarks prodcues a net charge of (2e)/(3) - e/3 - e/3 = 0 . If the quarks are in motion they can produce a non-zero magnetic moment. As a very simple model, suppose the u quark moves in a counter clockwise circular path and the d quarks move in a clockwise circular path, all of the radius r and all with the same speed v see figure. Determine the magnitude of the magnetic moment due of the circular u quark :-