why does a smple dc motor would have a non vanishing potential difference across the terminals as it is used and the current flows through it even if its rotor has a negligible resistance?
why does a smple dc motor would have a non vanishing potential difference across the terminals as it is used and the current flows through it even if its rotor has a negligible resistance?
a.Different sides of the rotor have dfferent distances from the ground
corresponding to di erent gravitational potential energies. When it
rotates, the non-vanishing potential di erence across the motor termi-
nal compensates for changing gravitational potential energy.
b.Positive and negative charges in a rotor are affected in different ways
when it rotates upon application of electricity. Whereas negative
charges cannot move, the positive charges can, causing a potential
di erence due to their net separation.
c.The potential difference across the terminals of a motor is simply
the applied voltage from a suitable source, presumably with non-zero
value.
d.As the rotor rotates, it couples with the external magnet supplying the
magnetic eld. This coupling creates a drag in the motion of charges
in the rotor. The drag corresponds to internal resistance that in turn,
corresponds to voltage.
e.A motor converts electrical energy to
input P = IV , where V is the potential di erence, cannot be zero.
There should then be a non-vanishing V to push the charges in the
rotor, for the motor to perform a meaningful amount of work.
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