Space charge and dielectric response in polar fluids

The assumption of "low signal" response is important in relation to the interpretation of the interaction of the electrical field (dc and ac) with mobile charge carriers. The existence of such a response is assumed in linear samples under the condition of absence of space charge. Experimental evidence as well as theoretical arguments of formation of hetero-charge in liquid-like materials have been reported. The materials, of course, are of low electrical conductivity. It has been demonstrated that the existence of space charge field is not always followed by sample nonlinearity. It is the case, where space charge field acts as a macrodipole with particular time or frequency response function. In principle, dc and ac sample responses should be the same because of the lack of nonlinearities. However, there is experimental evidence that this statement is not always true. The important problem seems to be the detection of space charge effects, which is particularly difficult in the case of ac measurements. There is a proposal to use dc combined with ac or dc measurements.