Kirchhoff’s Laws—
Kirchhoff gave two laws
Kirchhoff’s First law or Junction Law or Kirchhoff’s Current Law (KCL)
This law states that at a junction, the algebraic sum of all the currents is zero. In other words at a junction the sum of all the incoming currents is equal to the sum of all the outgoing currents.
Electric Energy—
The energy of a voltage source to flow a constant current through a resistor for a given time is called Electric Energy consumed in the circuit.
Let a voltage source ‘V’ supplies current ‘I’ through a resistor ‘R’, then 
The unit of Electrical Energy is ‘Watt-second’.
Heating Effect of Current--
When a resistor is connected with a voltage source, electrons start flow from negative electrode to positive electrode through this resistor and energy of the source gets dissipated in the form of heat produced in the resistor. This phenomenon is called heating effect of current.
Let we have a resistor ‘R’ which is connected to a Battery of voltage ‘V’ so that current ‘I’ flows Through it. Amount of charge flows through R in time t(q)=It
Amount of work done to flow charge ‘q’ through Resistor (W) = qV
Superconductivity—
As we know the velocity of the electrons in the conductors increase as the temperature increase, so, the number of collision between the electrons also increases. As a result resistance of the conductor also increases. This relation is given by