स्लिप रिंग इंडक्शन मोटर में निम्नलिखित में से किस स्टार्टिंग तकनीक का उपयोग किया जाता है?

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 __________.