If the primary winding of the transformer in the power supply opens what will you observe in the rectified output?

There would be no rectified output. The transformer primary has to be closed to induce a current into the secondary winding. At this point of the secondary the voltage is still AC. This voltage is then applied to the rectification bridge to change it to DC. So you can see how no voltage on the primary, the same as the unit being unplugged, affects the output voltage.