Question: what is the purpose of a dielectric material used in a capacitor
[{'answer': 'insulator', 'provenance': [{'wikipedia_id': '41026', 'title': 'Dielectric', 'start_paragraph_id': 1, 'start_character': 55, 'end_paragraph_id': 1, 'end_character': 64, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '41026', 'title': 'Dielectric', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 652, 'bleu_score': 0.9792717993254391, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13677456205416396435}, 'section': 'Section::::Terminology.\n'}]}]