in which K = coulombs discharged; P = periodic time of vibration of
needle; A = amperes producing a steady deflection equal to aº ; kº =
first angular deflection of needle. For accuracy kº and aº should both
be small and the damping so slight as to be negligible. Otherwise a
correction for the latter must be applied. For approximate work for kº
and aº the deflections read on the scale may be used with the following
formula: