यदि 230 V D.C. श्रेणी (सीरीज) मोटर को 230 V A.C. आपूर्ति से जोड़ दिया जाए तो क्या होगा?

What is the coupling field commonly used between electrical and mechanical systems in electromechanical energy conversion devices?

In a DC shunt motor operating at rated voltage, if the field flux is reduced to 70% of its nominal value while keeping the armature current constant, the percentage increase in speed (assuming negligible armature reaction) is approximately __________.