Units and Measurements

A temperature difference can generate e.m.f. in some materials. Let S be the e.m.f. produced per unit temperature difference between the ends of a wire, the electrical conductivity and the thermal conductivity of the material of the wire. Taking M, L, T, I and K as dimensions of mass, length, time, current and temperature, respectively, the dimensional formula of the quantity Z= S2 is:

1. [M0L0T0I0K0]
2. [M0L0T0I0K-1]
3. [M1L2T-2I-1K-1]
4. [M1L2T-4I-1K-1]

A dimensionless quantity is constructed in terms of electronic charge e, permittivity of free space 0, Planck's constant h, and speed of light c. If the dimensionless quantity is written as e 0 h c and n is a non-zero integer, then ( , , , ) is given by

1. (2n,-n,-n,-n)
2. (n,-n,-2n,-n)
3. (n,-n,-n,-2n)
4. (2n,-n,-2n,-2n)