Voltage Divider and Current Divider Rule.pptx

Voltage Divider and Current Divider

1. Voltage Divider and Current Divider Rule

2. Voltage Division Rule A series circuit acts as a  voltage divider  as it divides the total supply voltage into different voltages across the circuit elements. Figure shows a voltage divider circuit in which the total supply voltage  V  has been divided into voltages  V 1  and  V 2  across two resistances  R 1  and  R 2 . Although , the current through both resistances is same, i.e.,  I .

3. Voltage Division Rule As per Ohm’s law, V1 = IR1; V2 = IR2 Total Resistance R = R1 + R2 ----(1) V=IR = I (R1+R2) ---- (2) But I = = ----- (3 ) From Eqn (2) & (3), we have V = (R1 + R2) V1 = ----- (4)   Similarly, V = (R1 + R2) V2 = ----- (4 ) Hence, from equations of voltage division rule, it may be said that the voltage across a resistor in a series circuit is equal to the product of the value of that resistor and the total supply voltage, divided by the total resistance of the series resistors.  

4. Practice Problem 2 Find the voltage across resistors  R 1  and  R 2  in the circuit

5. Three resistive elements of 6kΩ, 12kΩ and 18kΩ are connected together in series across a 36 volt supply. Calculate, the total resistance, the value of the current flowing around the circuit, and the voltage drops across each resistor.

6. Current Divider Rule A parallel circuit acts as a  current divider  as it divides the total circuit current in its all branches. Figure shows a current divider circuit in which the total circuit current  I  has been divided into currents  I 1  and  I 2  in two parallel branches with resistances  R 1  and  R 2 . Although , we can notice that the voltage drop across both resistances is same, i.e.,  V .

7. Current Divider Rule According to Ohm’s law, I1 = I2 = Let R be the equivalent Resistance of the above circuit. R = ------ (1) From the circuit, I = V x ------ (2 ) Voltage across both the resistances are equal. V = I1R1 = I2R2 ---- (3)   From eqn (2) & (3), I = I1R1 = I1 I1 = ----- (4) Similarly, I = I2R2 = I2 I2 = ----- (5 ) Equations (4) and (5) give the expressions of current division rule. From these equations, we may state that the current in any of the parallel branches is equal to the ratio of opposite branch resistance to the sum of all resistances, multiplied by the total circuit current.  

8. Practice Problem 1 Find the currents  I 1  and  I 2  in the parallel circuit

9. Calculate the current flow in each branch of the circuit shown below: