A rod of mass m and length 2l is connected to two massless strings as shown in figure. A wooden disk of sme mass m is fixed at mid point of rod in such a way that plane of disk is perpendicular to the rod. A massless wire is wrapped around disk and having current I. There is vertically upward magnetic field B at the location of disk.
Answers
Answer:
The question is completely based on equilibrium you can watch it here.
Explanation:
Given:
A rod of mass m and length 2l is connected to two massless strings as shown in figure.
To find:
The tension in the string P
Solution:
From given, we have,
The tensions in the strings P and Q is given as,
Tp + Tq = 2mg ....(a)
The tensions in the strings P and Q in terms of the lengths of the strings are given as,
Tp (l) = Tq (l) + I (πR²) B
where l is the length of the strings, πR² is the area of the disk, where R is the radius of the disk, I is the current in the wire and B is the vertically upward magnetic field at the location of the disk.
Tp - Tq = [I (πR²) B] / l ........(b)
combining the equations (a) and (b), we get,
2Tp = 2mg + [I (πR²) B] / l
Tp = mg + [I (πR²) B] / 2l
∴ The tension in the string P is mg + [I (πR²) B] / 2l