# Homework problem

#### recca02

Joined Apr 2, 2007
1,214
good to hear that,
feel free to post for any further doubts,
next time onwards i'll try to put in more punctuations.

#### AlmostGenius13

Joined Aug 27, 2007
1
Hi Jut, I looked at this circuit for two days now...anyhow...if KVL is applied then don't we have to take i3 in acoount?
For loop 1 "i1" that 2Ohm resistor is also sahring some of the current of i3 isn't it???
Any suggestions anyone?

AlmostGenius13

#### recca02

Joined Apr 2, 2007
1,214
it was taken into account.

#### Newton1Law

Joined Aug 22, 2007
10
Your loop equations do not take into account the loop current I3. The equations are not quite complete. Look at the following and compare to your equations.

For I1:

80-2(I1-I3)-12I1=0

For I2:

80-8(I1+I3)-4I2=0

For I3:

-2I1+2I#+8I3+8I2+4I3=0

Simplify and get:

Equation (1) 80=14(I1) - 2(I3)

Equation (2) 80= 12(I2) + 8(I3)

Equation (3) 0=-2(I1) + 8(I2) + 14(I3)

Add equations (1) and (2) to make equation (4).

Solve Equation 1 for I3 to make equation (5).

Place the results for equation (5) into Equations (3) & (4)

Elimate (I2) by multiplying one of the equations such that the factor in fornt of I2 is equal in magnitude and opposite in sign. Add the equations together to remove I2 and solve for I1 which will equal 5 amps. V then is 5 amps X 4 Ohms = 20 volts.

Hope this helps.

#### Mr-Synapse

Joined Nov 1, 2006
5
Hello,
The main problem with your Loop equations is that they are not setup correctly.

You need to include the adjacent loop's affect on the Loop your writing. For Example your Loop 1. should include factor's from not only itself but the affects contributed by loops 2. & 3.

TIP:whenever a loop equation is written first include terms for the primary loop, then include the adjacent's loop's terms.

If you setup your equations properly then you should have no problem solving the corresponding Matrix.

#### anil.embsys

Joined May 14, 2008
1
Hii JUT,

Use Nodel analysis... it will give 2 equations only.........

Let us take left end node point voltage as v1 and other end v2

now equations are like this.....

v1/4+(v1-v2)/4+(v1-80)/8 = 0 --------------(1)
v2/12+(v2-v1)/4+(v2-80)/2 = 0 --------------(2)

By solving these two we can voltages at 2 nodes...... then u can calculate ur needed values

#### rashki

Joined Oct 8, 2009
1
See the scan pdf for solution. You need to write down mesh current equations and solve them.

Thanks,

rashki

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#### beenthere

Joined Apr 20, 2004
15,819
rashki - the original thread is 2 years old. Check dates.

#### t_n_k

Joined Mar 6, 2009
5,455
See the scan pdf for solution. You need to write down mesh current equations and solve them.

Thanks,

rashki
Hi rashki,

Sure it's an old post - but I thought you might like my crazy solution without mesh/nodal equations or star-delta transformations.

rgds,
t_n_k

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#### Ratch

Joined Mar 20, 2007
1,070
jut,

That circuit has the same topology as a Wheatstone bridge. Loop analysis will solve it.

Ratch