In a Wheatstone bridge(see fig.), Resistances P and Q are approximately equal. When R = 400 $$\Omega $$, the bridge is balanced. On interchanging P and Q, the value of R, for balance, is 405 $$\Omega $$. The value of X is close to :

Three charges Q, + q and + q are placed at the vertices of a right-angle isosceles triangle as shown below. The net electrostatic energy of the configuration is zero, if the value of Q is :

In the circuit shown,


the switch S₁ is closed at time t = 0 and the switch S₂ is kept open. At some later time(t₀), the switch S₁ is opened and S₂ is closed. The behavior of the current I as a function of time 't' is given by :

The resistance of the meter bridge AB in given figure is 4 $$\Omega $$. With a cell of emf $$\varepsilon $$ = 0.5 V and rheostat resistance R_h = 2 $$\Omega $$ the null point is obtained at some point J. When the cell is replaced by another one of emf $$\varepsilon $$ = $$\varepsilon $$₂ the same null point J is found for R_h = 6 $$\Omega $$. The emf $$\varepsilon $$₂ is, :