Series Circuit
What is DC Series Circuit?
When all the resistive components of a DC circuit are connected end to end to form a single path for flowing current, then the circuit is referred as series DC circuit. The manner of connecting components end to end is known as series connection. Suppose we have n number of resistors $R_1$, $R_2$, $R_3$ . . . $R_n$ and they are connected in end to end manner, means they are series connected. If this series combination is connected across a voltage source, the current starts flowing through that single path. As the resistors are connected in end to end manner, the current first enters in to $R_1$, then this same current comes in $R_2$, then $R_3$ and at last it reaches $R_n$ from which the current enters into the negative terminals of the voltage source.
Fig. 1: Three resisters in DC series circuit.
$$V1 = I \times R_1$$
$$V2 = I \times R_2$$
$$V3 = I \times R_3$$
$$ \bbox[5px,border:1px solid red] {\color{blue}{V=V_1 + V_2 + V_3}}$$
$$ \begin{array} {rcl} V &=& V_1 + V_2 + V_3 \\
V & = & I\times R_1+I \times R_2+I \times R_3 \\
V &=& I (R_1 + R_2 +R_3) \\
V &=& I \times R_T \end{array}$$
$$\bbox[5px,border:1px solid red] {\color{blue}{R_T = R_1+R_2+R_3}}$$
- The manner in which the supply is connected determines the direction of the resulting conventional current.
- The current is the same at every point in a series circuit.
- The polarity of the voltage across a resistor is determined by the direction of the current.
- The applied voltage is the sum of all the voltage drops.
- The circuit can be reduced to one Total Resistor which is the sum of all the resisters in series.
- The difference of voltage drop value depends upon the value of resistors.
- If one of the resistor cuts off, current flow would stop in the circuit.
Example 1: For the series circuit in Fig. 2:
a. Find the total resistance $R_T$.
b. Calculate the resulting source current $I$.
c. Determine the voltage across each resistor.
Solution: a: $R_T = R_1 + R_2 +R_3$
b: $E = I \times R_T$
c: $ V_1 = IR_1 = (1)(2) = 2 V$
a. Find the total resistance $R_T$.
b. Calculate the resulting source current $I$.
c. Determine the voltage across each resistor.
Fig. 2: Series circuit to be analyzed in the example 1.
Solution: a: $R_T = R_1 + R_2 +R_3$
$$R_T = 2+3+5 = 10Ω$$
$$I = {E \over R_T} ={10 \over 10} = 1A$$
$$ V_2 = IR_2 = (1)(3) = 3 V$$
$$ V_3 = IR_3 = (1)(5) = 5 V$$
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