The total charge enclosed in an incremental volume of 2 $$\times$$ 10^$$-$$9 m³ located at the origin is ___________ nC, if electric flux density of its field is found as

D = e^$$-$$x sin y $$\widehat i$$ $$-$$ e^$$-$$x cos y $$\widehat j$$ + 2z $$\widehat k$$ C/m²

The position of the centre of mass of a uniform semi-circular wire of radius 'R' placed in x-y plane with its centre at the origin and the line joining its ends as x-axis is given by $$\left( {0,{{xR} \over \pi }} \right)$$. Then, the value of | x | is ______________.

In an electric circuit, a cell of certain emf provides a potential difference of 1.25 V across a load resistance of 5$$\Omega$$. However, it provides a potential difference of 1 V across a load resistance of 2$$\Omega$$. The emf of the cell is given by $${x \over {10}}V$$. Then the value of x is ______________.

The area of cross-section of a railway track is 0.01 m². The temperature variation is 10$$^\circ$$C. Coefficient of liner expansion of material of track is 10^$$-$$5/$$^\circ$$C. The energy stored per meter in the track is ____________ J/m.

(Young's modulus of material of track is 10¹¹ Nm^$$-$$2)