If a charge $$q$$ is placed at the center of the line joining two equal charges $$Q$$ such that the system is in equilibrium then the value of $$q$$ is

The mass of product liberated on anode in an electrochemical cell depends on (where $$t$$ is the time period for which the current is passed).

A wave $$y=a$$ $$\sin \left( {\omega t - kx} \right)$$ on a string meets with another wave producing a node at $$x=0.$$ Then the equation of the unknown wave is

If in the circuit, power dissipation is $$150W,$$ then $$R$$ is