Magnetic effect of current practice · Mixed difficulty

A galvanometer with its coil resistance $25\Omega$ requires a current of 1mA for its full deflection. In order to construct an ammeter to read up of a current of 2A, the approximate value of the shunt resistance should be

A horizontal overhead power line carries a current of $90 \mathrm{~A}$ in east to west direction. What is the magnitude and direction of the magnetic field due to the current, $1.5 \mathrm{~m}$ below the line?

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason
R.
Assertion A: For measuring the potential difference across a resistance of $600 \,\Omega$, the
voltmeter with resistance $1000 \,\Omega$ will be preferred over voltmeter with resistance $4000\,\Omega.$
Reason R: Voltmeter with higher resistance will draw smaller current than voltmeter with lower resistance.
In the light of the above statements, choose the most appropriate answer from the options given below:

A moving coil galvanometer has $N$ number of turns in a coil of effective area $A$, it carries a current $I$. The magnetic field $B$ is radial. The torque acting on the coil is

Statement A: When a proton and a neutron enter into a transverse magnetic field with equal speeds, then they trace circular paths of equal radii.
Statement B: In a transverse magnetic field the period of revolution of a charged particle in a circular path is directly proportional to the mass of the particle.

Two particles having same charge and K.E enter at right angles into the same magnetic field and travel in circular paths of radii 2cm and 3cm respectively. The ratio of their masses is

The earth’s magnetic induction at a certain point is $7 \times {10^{ - 5}}\;\mathrm{Wb}{\mathrm{m}^{ - 2}}$. This is to be annulled by the magnetic induction at the center of a circular conducting loop of radius 15 cm. The required current in the loop is

Assertion (A): In ammeter, current in shunt is always greater than current in galvanometer.

Reason (R): Value of shunt resistance may be smaller than galvanometer resistance and is parallel to it.

In a region an electron is moving in a circle. What can be the possible field there?

Three moving coil galvanometers are made of coils of three different material having torsional constant $1.8\,\, \times \,\,{10^{ - 8}},\,\,2.8\,\, \times \,\,{10^{ - 8}}$and $3.8\,\, \times \,\,{10^{ - 8}}$ respectively. If the three galvanometers are identical in all other respect, then in which of the above cases sensitivity is maximum?