Soap operas are characterised by romance,sentimentality and melodrama (Passive Voice) → Romance, sentimentality and melodrama characterise soap operas (Active Voice)
The term 'soap opera' was coined by the American press in the 1930s because these serials were sponsored by soap manufacturers (Passive Voice) → The American press coined the term 'soap opera' in the 1930s because soap manufacturers sponsored these serials.
The serials were mainly watched by women (Passive Voice) → Women mainly watched the serials (Active Voice)