Question

A wire frame in the form of a tetrahedron ADCB is connected to a d.c. source

Answer 1

The total resistance (RAB) of the frame can be calculated easily from the symmetry considerations. There would no current in edge CD.

As we know, RAB = R/2, where R = resistance of edge.

Hence, I = 2U/ R, where U = applied voltage.

Total current is changed in 2 ways i.e. if one of the edges BC, AD, AC or BD is removed, the change in current would be the same. If edge AB is removed, the change would be different.

In the 1st case, the change will be ΔI = -(2/5) U/R = -I/5, and in 2nd case, the total resistance = R, and hence ΔI = - U/R = -I/2 = ΔImax.