Magnetic Force, Torque and Galvanometer Quiz

Which of the following represents the correct design of galvanometer?

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When the pointer of the galvanometer stops, the torsion of the spiral springs will be ...........

• BIAN

• BIAN sin θ

• Zero

• 1/2 (BIAN)

A rectangular coil made of insulated wire, its dimensions are 0.1 m and 0.05 m, consists of 50 turns, can rotate in a magnetic flux of 10^-3 wb perpendicularly to the coil plane , around an axis in the same plane of its surface that is parallel to its length. If a current of 2 A passes through the coil so, the value of the magnetic torque acting on the coil equal to ........

• 0.1 N .m

• zero

• 5 x 10^-4 N .m

• 2 x 10^-3 N .m

To increase the sensitivity of the Galvanometer, ............

• Use soft iron

• Use weak spring

• Use jewelled bearing

• All correct answers

From the data in the figure, which of the following choices represents the correct arrangement of magnetic forces per unit length acting on each wire?

• F_x < F_y < Fz

• F_y < F_x < F_z

• F_z < F_y < F_x

• F_y < F_z < F_x

In the opposite figure: at which point a straight wire carry current may be placed on the same plane of the page and parallel to the two wires (X) and (Y) so that it doesn’t affect by a magnetic force

• M

• N

• L

• K

Wire (X) carries current (I), which is put in different magnetic fields, so the magnetic force that affect wire (X)

• F₁ > F₂ > F₃ > F₄

• F₁ > F₂ = F₃ = F₄

• F₂ > F₃ > F₁ = F₄

• F₂ = F₃ > F₁ = F₄

An electric motor; contains rectangular coil that rotates starting from the position which was parallel to the magnetic flux lines, When the coil rotates by an angle 60 ̊ clockwise, ................

• The torque remains constant

• The force that affect side bc becomes half its value

• The force that affect side ab remains unchanged

• The torque become 0.866 of its value

You have two galvanometers, the current (I) pass in each, so the pointer of 1st galvanometer deflects by an angle of 30° and the 2nd galvanometer deflect by 10 degrees more than that of the first, when the current is increased to (2I), which of the following statements is true after increasing the current to 2I in each of them?

• The angle of deviation of the first device is equal 20°

• The sensitivity of the first device 60/I

• The sensitivity of the second device 40/I

• The angle of deviation of the second device is equal 40°

Two long parallel wires X and Y , each of them is connected to a battery of negligible internal resistance , the mutual force between them is (F) . When wire X is replaced by another one of same length and radius but the resistivity of its material is 1/4 of that of wire X so, the mutual force between the two wires becomes ………………….

• 2F

• F

• 4F

• F/4