In: Physics
A 10.0-cm side square loop is fashioned from a single 4.00-m long, 100-g wire. One side of the loop is attached to a horizontal, frictionless axle. The loop is suspended in a region with a uniform 10.0-mT magnetic field oriented vertically. (a) What angle does the loop make with the vertical when it carries a current of 3.40 A? (b) What magnetic torque acts on the loop?
Imagine a loop attached to a rod(Axle) along one of its sides. Now its suspended by the axle and its hanging vertically. Now the current carrying loop being suspended in an external magnetic field experiences a force
where i: current in the loop, l: length of the current carrying wire of which the force is calculated, B: magnetic field
The force acts only on the horizontal sides of the loop, as for the vertical sides the length vector and magnetic field vector are parallel to each other; in horizontal case the vectors are perpendicular.
here
m=10g (from 4m of wire wieghing 100g, calculating how much 40 cm weighs)
is the angle made by the loop with the vertical.
(b)
Torque on the loop is given by,
angle between area vector and magnetic field is 90 degrees.
is the torque acting on the loop.