#### Physics (NTSE/Olympiad)

# 1. Electricity

__Combination Of Resistances__

**Law of Combination of Resistances** :

In an electric circuit, the components are connected in several types of combinations. The two different ways called series and parallel combination circuits. In a series combination of the electric circuit, the electric current passes through each of the components of the circuit, and its voltage across the circuit is the sum of the voltages across the component. In the parallel combination of a circuit, the voltage across each component is the same and the total current is the sum of the currents through each component.

**Series Combination **
When two or more resistances are joined end-to-end so that the same current flows through each of them, they are said to be connected in series.

When a series combination of resistances is connected to a battery, the same current (I) flows through each of them.

**The Law of a combination of resistances in series:**
The law of combination of resistances in series states that when a number of resistances are connected in series, their equivalent resistance is equal to the sum of the individual resistances. Thus, if R

_{1}, R

_{2}, R

_{3} ..., etc. are combined in series, then the equivalent resistance (R) is given by,

R = R

_{1} + R

_{2} + R

_{3} + ... ....(i)

In the next section of the combination of resistances, we can understand the

mathematical derivation of the resistance in series combination and examine the equivalent resistance results. In the combination of resistances, we can use the Ohm’s law and derived the desired formula for the series combination of a particular electrical circuit.