Efficiency of a Source—

The efficiency of a source is defined as the ratio of the output power to the input power.

Let a voltage source of emf ‘E’ and internal resistance ‘r’ is connected to the resistance ‘R’ so that current ‘I’ is flowing through it, then efficiency

Efficiency of an Electrical Device—

Electric Power—

The rate of work done by the voltage source to flow the current in the circuit is called electric power of the circuit or the rate of heat produced in the resistor is called its electric power.

Definition of One Watt—

If W= 1 J and t= 1s then P= 1W

If an appliance consumes one joule of energy in one second then its power is called one watt.

Combination of Cells—

Cells are combined in three manner

1. Series Combination
2. Parallel combination
3. Hybrid or Mix combination

Series Combination of Cells—       

When cells are arranged such that negative electrode of first cell is connected to the positive electrode of  the second cell and negative electrode of second one is connected to the positive electrode of third so on, the arrangement is called series combination.

Kirchhoff’s Laws—

Kirchhoff gave two laws

1. Kirchhoff’s First law or Junction Law or Kirchhoff’s Current Law (KCL)
2. Kirchhoff’s Second Law or Loop Law or Kirchhoff’s Voltage Law (KVL)

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