Edit: Corrections and details.
Thanks for your reply. I am sure I didnt mix them up. My voltmeter switches to DC or AC automatically. It shows 5.16 V DC at the 5V pin from Arduino when the display and IC2 module are not connected.
When they are connected, 4.7 V DC (but there is variation of around +- 0.05 V) at the Arduino 5V source, I2C's vcc and display's Vdd.