That
is, if the charge on the capacitor is, say  doubled,
the electric field will also be doubled at every point (This follows from the direct proportionality
between field and charge implied by Coulomb’s
law and the superposition principle ) Now,
potential difference V is the work done per unit
positive charge in taking a small test charge from
the conductor 2 to 1 against the field Consequently, V is also proportional to Q, and the
ratio Q/V is a constant:
Q
C
=V
(2