CIRCUIT THEORY

20EIT12

VOLTAGE DIVISION RULE

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In the field of electronics, a voltage divider is a basic circuit, used to generate a part of its input voltage like an output. This circuit can be designed with two resistors otherwise any passive components along with a voltage source. The resistors in the circuit can be connected in series whereas a voltage source is connected across these resistors. This circuit is also called a potential divider. The input voltage can be transmitted between the two resistors in the circuit so that the division of voltage takes place.

EXAMPLES AND APPLICATIONS OF VOLTAGE DIVISION RULE

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It is used to change a large voltage into a small voltage. Generally, these dividers are used to reduce the magnitude of the voltage or to create reference voltage and also used at low frequencies as a signal attenuator. For DC and relatively low frequencies, a voltage divider may be appropriately perfect if made only of resistors; where the frequency response is required over a wide range.

Voltage Divider Circuits are useful in providing different voltage levels from a common supply voltage. This common supply can be a single supply either positive or negative, for example, +5V, +12V, -5V or -12V, etc. with respect to a common point or ground, usually 0V, or it could be across a dual supply, for example ±5V, or ±12V, etc.

Voltage dividers are also known as potential dividers, because the unit of voltage, the “Volt” represents the amount of potential difference between two points. A voltage or potential divider is a simple passive circuit that takes advantage of the effect of voltages being dropped across components which are connected in series.

The potentiometer, which is a variable resistor with a sliding contact, is the most basic example of a voltage divider as we can apply a voltage across its terminals and produce an output voltage in proportion to the mechanical position of its sliding contact. But we can also make voltage dividers using individual resistors, capacitors and inductors as they are two-terminal components which can be connected together in series.

Voltage Divider Calculation

Let us consider the following circuit connected by using two resistors R1 andR2. 

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Current Dividers

Current Divider circuits have two or more parallel branches for currents to flow through but the voltage is the same for all components in the parallel circuit

Problem

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Apply voltage division rule to find voltage drop across 5Ω and 15Ω

Solution:

1. Req=20 Ω
2. V at 5 Ω=5V
3. V at 15 Ω=15V

Problem

By applying current division rule, find the current through 2Ω and 4 Ω

Solution :

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1. I1=6.667A
2. I2=3.33A

I3= (Ip*R2)/ (R2+R3)

= (20.59*2)/ (2+5)

I3= 5.88A

Four resistors of 2Ω, 3Ω, 4Ω and 5Ω respectively are connected in parallel . What Voltage must be applied to the group in order that the total power of 100Watts may be absorbed?

Three resistors are connected together to form a current divider circuit as shown below. If the circuit is fed from a 100 volts 1.5kW power supply, calculate the individual branch currents using the current division rule and the equivalent circuit resistance.

We can check our calculations as according to Kirchhoff’s Current Rule, all the branch currents will be equal to the total current, so: I_T = I_R1 + I_R2 + I_R3 = 10 + 4 + 1 = 15 amperes, as expected. Thus we can see that the total current, I_T is divided according to a simple ratio determined by the branch resistances. Also, as the number of resistors connected in parallel increases, the supply ot total current, I_T will also increase for a given supply voltage, V_S as there are more parallel branches taking current.

Reduce the network shown in the figure to a single resistance.

The equivalent resistance of four resistors joined in parallel is 30ohms. The current flowing through them are 0.5, 0.4, 0.6 and 0.1A. Find the value of

each resistor.

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