DC Circuits

DC CIRCUITPREPARED BY: 130400116023- Patel Nidhi Harkishnbhai130400116036- Sharma Surabhi Chandra DeoBE First Semester IT

ACTIVE LEARNING ASSIGNMENTS

DEPARTMENT OF ELECTRICAL ENGINEERINGSANKALCHAND PATEL COLLEGE OF ENGINEERING,VISNAGARGuided BY: Prof. P. R. Bhavsar DC CircuitsThe circuitResistance in combinationsKirchhoffs RulesRC transient circuits

Work done by a battery on charge Here

Real Battery and Single Loop circuits Whats the current ?

Conservation of energy: Kirchoffs first Law: Sum of voltages in a closed loop is zero.

Real Circuit with ammeter and voltmeter Equivalent ResistanceResistors in SeriesSeries requirementsConservation of energyPotential differences addCurrent is constant

Apply Ohms Law to each resistor

Resistors in parallelParallel requirementsCharge conservationCurrents must addPotential difference is same across each resistor

Apply Ohms Law to each resistor

Example 1

What is current through battery?What is current through i2 ?Kirchhoffs RulesThe algebraic sum of the currents entering a junction is zero. (Conservation of Charge)

The algebraic sum of the changes in electric potential difference around any closed circuit loop is zero. (Conservation of Energy)

Signs for Rule 2The direction of travel when traversing the loop is from a to b.Problem 2

Find the currents in each of the three legs of the circuit,

Three unknowns, need three equations. Also since batteries are in there cannot reduce the resistances since none in parallel or seriesExample: Applying Kirchhoffs RulesApply Kirchhoffs first rule to the three wire junction at the bottom of the diagram

Apply Kirchhoffs second rule to the closed path in red, traversing it clockwise

Apply Kirchhoffs second rule to the closed path in green, traversing it clockwiseNote the sign changes for some of the elements

Another, example: applying Kirchhoffs Rules Solve the equations simultaneously for the values if I. If I is negative the current is in the opposite direction

RC Circuits and Time dependence

Time dependence Resistor slows down the charging of the capacitor Time dependent behavior (transient) 2 cases: switch at a or at b

ChargingdischargingIn position a Charging the CapacitorUse Kirchhoffs Loop rule

Or the voltage across capacitor is ..

Whats VR across resistor?Find the current and multiply by R

Discharging Position b:Example: RC circuit How long does it take the capacitor to reach its final charge, if the capacitor is uncharged at t = 0?

R=10C=1F

1. Charging the Capacitor

Note:

is called the time constant