  We extensively investigate the electronic and transport properties of a
twisted bilayer graphene when subjected to both an external perpendicular
electric field and a magnetic field. Using a basic tight-binding model, we show
the flat electronic band properties as well as the density of states (DOS),
both without and with the applied electric field. In the presence of an
electric field, the degeneracy at the Dirac points is lifted where the
non-monotonic behavior of the energy gap exists, especially for twist angles
below 3$^\circ$. We also study the behavior of the Landau levels (LL) spectra
for different twist angles within a very low energy range. These LL spectra get
modified under the influence of the external electric field. Moreover, we
calculate the dc Hall conductivity ($\sigma_{xy}$) for a very large system
using the Kernel Polynomial Method (KPM). Interestingly, $\sigma_{xy}$ makes a
transition from a half-integer to an integer quantum Hall effect, \textit{i.e.}
the value of $\sigma_{xy}$ shifts from $\pm 4(n+1/2) (2e^2/h)$ ($n$ is an
integer) to $\pm 2n (2e^2/h)$ around a small twist angle of
$\theta=2.005^\circ$. At this angle, $\sigma_{xy}$ acquires a Hall plateau at
zero Fermi energy. However, the behavior of $\sigma_{xy}$ remains unaltered
when the system is exposed to the electric field, particularly at the magic
angle where the bands in both layers can hybridize and strong interlayer
coupling plays a crucial role.
