A rotary potentiometer has a circular resistance (C) and a conducting wiper (W) can rotate over it. An ideal battery and an ideal voltmeter are connected to it as shown in the figure. As the wiper is rotated on the circular resistance the reading of the voltmeter changes from zero to `20 V`. What is reading of the voltmeter when wiper is at angular position `theta = 120^(@)` ? Assume that resistance C is almost a complete circle and resistance of all connecting wires and knobs in the circuit is zero.
