Physics - Magnetic Effects of Currents

Question - 1

An electron is injected into a region of uniform magnetic field of induction with its velocity inclined to the field. The path of the electron is a

• A circle
• B parabola
• C linear
• D helix

Question - 2

The sensitiveness of a moving coil galvonometer can be increased by

• A decreasing the area of the coil
• B decreasing the number of turns in the coil
• C increasing the area of the coil
• D increasing the strength of the current

Question - 3

When a charged particle moves in a crossed electro-magnetic field with a velocity $\vartheta$ without deviation, then

• A $\vartheta$ is constant and it is proportional to field
• B $\vartheta$ is constant and it is inversely proportional to field
• C $\vartheta$ is equal to ratio of electric field to magnetic field
• D $\vartheta$ is equal to ratio of magnetic field to electric field

Question - 4

A circular coil carrying current has magnetic induction B at its centre C. The radius of the coil is 3 cm. The distance of a point P from C, where the induction reduces to $\frac { B }{ 8 }$ would be

• A $\sqrt { 3 }$
• B 2$\sqrt { 3 }$
• C 3$\sqrt { 3 }$
• D 9

Question - 5

Two infinite long wires at a distance of 1 m carry current of 1 mA in the same direction. Which one of the following is CORRECT?

• A The given two wires repel each other
• B Both wires experiences a force exactly equal to 2 X 10-7 Nm-1
• C One of the two wires is replaced by an electron beam, then beam will not get deflected
• D NONE OF THESE

Question - 6

A galvanometer can be used to measure voltage drop when it is connected with

• A high resistance in series with it
• B a high resistance in parallel with it
• C a low resistance in series with it
• D a low resistance in parallel with it

Question - 7

A ballistic galvanometer

• A measure charge and it has small moment of inertia
• B measures current and it has small moment of inertia
• C measures charge and it has large moment of inertia
• D measures current and it has large moment of inertia

Question - 8

A particle of charge q at a velocity $\vartheta$  moves in a circular path of radius r in a region of uniform magnetic field B. The work done by the magnetic field on the particle is

• A zero
• B equal to charge in kinetic energy
• C $2\pi q\vartheta Br$
• D $q\vartheta Br$

Question - 9

For a good voltmeter (moving coil type),

• A both internal resistance and moment of inertia are large
• B both internal resistance and moment of inertia is small
• C internal resistance is large but moment of inertia is small
• D internal resistance is small but moment of inertia is large

Question - 10

The electron of Bohr orbit of hydrogen atom revolves in its innermost orbit round the proton. The magnetic induction at the proton is of the order of

• A 1 T
• B 10 T
• C 100 T
• D 1000 T