Motional Emf

From NCERT Class 12, Chapter 6 (Electromagnetic Induction), a conductor of length $l$ moving with velocity $v$ perpendicular to a magnetic field $B$ develops a motional emf given by $\epsilon =Blv$, arising because the magnetic force on free electrons in the rod separates charge until an electrostatic field balances it. Substituting the given values: $\epsilon =0.8\times 0.5\times 4=1.6\text{V}$. The option 0.4 V wrongly divides rather than multiplies one of the factors. The option 3.2 V doubles the length or velocity incorrectly. The option 2.0 V results from misusing 5 m/s or an arithmetic slip. As a sanity check, the units combine as $\text{T}\cdot \text{m}\cdot \text{m/s}=\text{V}$, since $1\text{T}=1{\text{Vcdotps/m}}^2$, confirming the dimensional consistency of the answer, and a value of a few volts is physically reasonable for these modest laboratory quantities.