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VADODARA INSTITUTE OF ENGINEERING
KOTAMBI-391510
ACTIVE LEARNING ASSIGNMENT
ON
SUBMITTED BY
Parth sandesara-13ELEE533

Foram sureja-13ELEE531
 Vivek lakhana-13ELEE532

Sahaj patel-13ELEE534
Direct Current Circuits
Chapter 1
Sources of emf

The source that maintains the constant
current in a closed circuit is the emf.

Batteries, & generators are two sources of
emf

They increase the PE of the charges
circulating in the circuits
Sources of emf

DV = E – Ir



r = the internal resistance of the battery
DV = the terminal voltage of the battery
I = E /( R + r )

If R is much greater than r, we can neglect r
in our analysis and we do, for many circuits
Sources of emf

IE = I2R + I2r



This tells us the total power output of the
source of emf
If R is much greater than r, than most of the
power from the emf is transferred to the load
resistance
We will assume that the internal
resistance, r, of a battery is negligible.
Resistors in Series

Series



The current through any combination of
resistors in series is constant
The voltage drop across an individual resistor
in series is variable.
Req = R1 + R2 + R3 + . . .
Resistors in Series
Fig. 18.2b, p. 557
Slide 6
Resistors in Parallel

Parallel



The current through each resistor connected
in parallel is variable (path of least resistance)
The voltage across each resistor connected
in parallel is constant.
1/Req = 1/R1 + 1/R2 + 1/R3 + . . .
Resistors in Parallel
Fig. 18.6b, p. 560
Slide 13
Kirchoff’s Rules

The sum of the currents entering any junction
must equal the sum of the currents leaving that
junction.


(Junction Rule)
The sum of the DV across all the elements
around any closed-circuit loop must be zero.

(Loop Rule)
Kirchoff’s Rules



You must assign symbols and directions to the
currents.
When applying the loop rule, you must choose a
direction for going around the loop.
DV = I1R1 + I2R2 + I3R3

Use a system of equations to solve for the missing
quantity
Kirchoff’s Rules
Fig. 18.14, p.565
Slide 27
RC Circuits

In RC circuits the current varies with time

q = Q(1 – e(-t/RC))




Q is the maximum charge
t = time
RC is the time constant called t
The time constant, t, represents the time
required for the charge to increase from zero to
63.2% of its maximum value
RC Circuits

Discharging of a capacitor


q = Qe(-t/RC)
In one time constant the capacitor loses
63.2% of its initial charge