Electrical Engineering - Circuit Theorems and Conversions - Discussion
Discussion Forum : Circuit Theorems and Conversions - General Questions (Q.No. 1)
1.
Find the Thevenin equivalent (VTH and RTH) between terminals A and B of the circuit given below.
4.16 V, 120 
41.6 V, 120
4.16 V, 70
41.67 V, 70
Discussion:
42 comments Page 2 of 5.
Nagesh said:
9 years ago
The resistances 68 and 100 are in series ; 68 + 100 = 168.
168 ohms is in parallel with 120 ohms. So,
Rth = (168 * 120) / (168 + 120) = 70 ohms.
Vth = R3 * (Vs/R1 + R2 + R3).
Vth = 41.67V.
168 ohms is in parallel with 120 ohms. So,
Rth = (168 * 120) / (168 + 120) = 70 ohms.
Vth = R3 * (Vs/R1 + R2 + R3).
Vth = 41.67V.
(11)
T.Ramachandran said:
9 years ago
Vth = the voltage across the 120 Ohms. this is calculated by determining the current in the loop by applying KVL.
The KVL in the loop is,
100 - 68I - 100I - 120I = 0
=> 100 = 68I + 100I + 120I
=> I = 100/288
=> I = 0.347A
and,
Vth = 120 * I
Vth = 120 * 0.347 = 41.67V
To find Rth,
68 and 100 in series and this series combination come in parallel with 120 Ohms.
So,
Rth = (168*120/168+120)
Rth = 58.33 Ohms.
The KVL in the loop is,
100 - 68I - 100I - 120I = 0
=> 100 = 68I + 100I + 120I
=> I = 100/288
=> I = 0.347A
and,
Vth = 120 * I
Vth = 120 * 0.347 = 41.67V
To find Rth,
68 and 100 in series and this series combination come in parallel with 120 Ohms.
So,
Rth = (168*120/168+120)
Rth = 58.33 Ohms.
(1)
Aaron said:
10 years ago
In what world is R3 parallel to R1 and R2? they look in series to me. It is parallel to the load yet, but not with R1 and R2. The definition of parallel connection is that it shares two or more nodes, and this simply does not. I am confused.
Naveen said:
10 years ago
Rth = 168.
Vth = 100 V.
Vth = 100 V.
Anshu said:
10 years ago
When we have to find the venin voltage b/w two terminal then, firstly we have to remove the load resistance b/w these terminal. So why all are considering r3?
Prabha said:
1 decade ago
I can't understand.
Thangam said:
1 decade ago
I need simple formula for solving these circuit analysis.
Khinya Ram Choudhary said:
1 decade ago
Let R = R1+R2;
Rth = R||R3;
According to Thevenin Theorem:
Rth = (168*120/(168+120)) = 70 Ohm.
Vth is Thevenin voltage Between A&B,
According to Voltage Divider Rule:
Vth = Vs*R3/ (R+R3).
= 41.67 V.
Rth = R||R3;
According to Thevenin Theorem:
Rth = (168*120/(168+120)) = 70 Ohm.
Vth is Thevenin voltage Between A&B,
According to Voltage Divider Rule:
Vth = Vs*R3/ (R+R3).
= 41.67 V.
K.Hanumantha said:
1 decade ago
Friends.
According to Thevenin theorem voltage should be short while calculating of resistor Rth, when we do that, R3 is parallel with (r1+r2). So equivalent, 168//100 = 70 ohm Rth.
Vth = r3*I. where I = Vs/(r1+r2+r3) = 100/(68+100+120) = 0.3472A.
We need Vth = I*r3 = 0.3472*120 = 41.67V.
According to Thevenin theorem voltage should be short while calculating of resistor Rth, when we do that, R3 is parallel with (r1+r2). So equivalent, 168//100 = 70 ohm Rth.
Vth = r3*I. where I = Vs/(r1+r2+r3) = 100/(68+100+120) = 0.3472A.
We need Vth = I*r3 = 0.3472*120 = 41.67V.
Akshit raulji said:
1 decade ago
First of all open 120 ohm resistance because Vth is find across it so it should be open than applied voltage divider rule.
Vth = 100*68/(68+100). So we get 40.47v.
Vth = 100*68/(68+100). So we get 40.47v.
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