PARALLEL CIRCUIT

• parallel circuit is one that has two or more paths for the electricity to flow, the loads are parallel to each other. 
  

• if the loads in this circuit were light bulbs and one blew out, there is still current flowing to the others because they are still in a direct path from the negative to positive terminals of the battery.

 Advantages of parallel electrical circuits

Parallel circuits are the standard for home electrical wiring but we sometimes forget why. Did you know they offer four advantages over series circuits that help make our lives easier? Here's how.

• One of the advantages of parallel circuits is that they ensure all components in the circuit have the same voltage as the source. For instance, all bulbs in a string of lights have the same brightness.

• When you turn on one gadget and you don't necessarily want to turn on all the others, parallel circuits make it possible for different components to have their own switches.That means you can turn your appliances on or off independently of each other.

• Parallel circuits also allow components to be added in the circuit without changing the voltage. For example, if you want additional lighting, you can add a third or fourth light bulb, which you can turn on or off regardless of the other bulbs in the same circuit.

 Characteristics of Parallel Circuit

• Voltage across every parallel component is equal   VT = V1 = V2 = V3...
• The total resistance is equal to the reciprocal of the sum of the reciprocal.                                                

    1  =   1   +   1   +   1      or     RT=              1              

   RT     R1        R2       R3                          1   +   1   +   1   

                                                          R1       R2       R3   

• The sum of all currents in each branch is equal to the total current. This is called Kirchhoff's Current Law. IT = I1 + I2 + I3...

      If the power (W) and resistance present only I = √ P/R

Examples

.In the following schematic diagram, find the total current, total resistance. 

Solution:

The total voltage is  = 12.0 V

So, between points A and B, the potential must drop 12.0V. Also, the potential drop across branches of a circuit are equal. That is,    VT = V1 = V2 = V3  = 12.0v  

We can use Ohm's Law  V = IR  or  I = V/R   to find the current across each resistor.

• the total current is IT = 12.0A.

Computation in finding total resistance.

 1  =   1   +   1   +   1   

RT     R1        R2       R3  

 1  =   1   +   1   +   1   =    1    = 0.923 ohms

RT     2         3          4      1.083

• the total resistance is RT = 0.923 ohms

Computation in finding power.

P1 = I1V1 =   6(12) = 72W

P2 = I2V2 =   4(12) = 48W

P3 = I3V3 =   2(12) = 24W

PT = ITVT =12(12) = 144W

• the total power is PT = 144Watts