A girl has many resistors of 2 `Omega`each. She needs a circuit of `9 Omega` resistance . For this draw a circuit with the minium number of resistors.

10 resistors of 2 Omega each are connected in parellel. Calculate the effective resistance.

Impedance of a series LR circuit is 25 Omega . If the resistance is 20 Omega . Find the reactance.

A cell and two resistors R_1 and R_2 are provided to you. Derive an expression for the effective resistance of the circuit in which current is the same in both resistors.