21.A wire of resistance R is stretched so that its length increases by 10%. The resistance of the wire increases by

22.The plates of a capacitor are charged to a potential difference of V volts and then connected across a resistor. After one second, the potential difference between the plates is V/3, then after 2 sec. from the start, the potential difference between the plates is

23.When the cells of different e. m. fs. and internal resistances are connected in parallels

24.If internal resistance of cells is large as compared to the external resistance then the cells should be connected in

25.Two wires of equal length and material X and Y have same fesistance. The ratio of the radii of the two wires is 1 : 2. The ratio of the conductivity of X and Y is