Electrical Engineering - Circuit Theorems and Conversions - Discussion
Discussion Forum : Circuit Theorems and Conversions - General Questions (Q.No. 24)
24.
Referring to the given circuit, determine VTH and RTH if a 68 
resistor is connected in parallel across R2 and R3.
resistor is connected in parallel across R2 and R3.
3.3 V, 148
330 mV, 148
3.3 V, 68
330 mV, 68
Discussion:
6 comments Page 1 of 1.
Maya said:
1 decade ago
I'm not understand. How it is?
Kiran kishore said:
1 decade ago
Vth=12*38.35/100+38.35=3.327.
Rth=120+(100*38.35)/(100+38.35)=147.8(148 approx).
38.35=(68+20)*68/(88+68)
Be cause we connect a resistor parallel to R2 & R3.
Rth=120+(100*38.35)/(100+38.35)=147.8(148 approx).
38.35=(68+20)*68/(88+68)
Be cause we connect a resistor parallel to R2 & R3.
Pocahontas said:
1 decade ago
68 ohm resistor is in parallel with R2 and R3 meaning when we get the Rth ....100, 88(68+20), and 68 are all in parallel and the 120 resistor in series
(1/100 + 1/88 + 1/68)^-1 +120= 147.72 ohms or 148 ohms.
To get Vth use mesh analysis
We get the following equations:
188I1 -88I2 = 12.
-88I1 +156I2 = 0.
Solving simultaneously we get I2=0.048925.
0.048925*68 = 3.3V.
(1/100 + 1/88 + 1/68)^-1 +120= 147.72 ohms or 148 ohms.
To get Vth use mesh analysis
We get the following equations:
188I1 -88I2 = 12.
-88I1 +156I2 = 0.
Solving simultaneously we get I2=0.048925.
0.048925*68 = 3.3V.
Nivi said:
5 years ago
@Kiran Kishore.
How you got 38.35?
How you got 38.35?
Latha said:
4 years ago
@Nivi.
Given 68-ohm resistor is parallel across R2 and R3.
R2 + R3 = 68 + 20 =88.
Now 68 becomes parallel to 88, (68 || 88) solving this gives 38.35
68||88 = (68*88)/(68+88) = 38.35.
Given 68-ohm resistor is parallel across R2 and R3.
R2 + R3 = 68 + 20 =88.
Now 68 becomes parallel to 88, (68 || 88) solving this gives 38.35
68||88 = (68*88)/(68+88) = 38.35.
PinayFlix said:
2 years ago
In order to solve this problem you just need to imagine there is an 68-ohm resistor in parallel in the current 20-ohm and 68-ohm resistors that is in series.
If we solve for rth its going to be:
RTH = 68//(68+20)//100 + 120 = 148 ohms.
To solve for vth you need to use the current divider rule:
VTH = 12 [(12)*(68//88)/(68//88 + 100)] = 3.3 volts.
If we solve for rth its going to be:
RTH = 68//(68+20)//100 + 120 = 148 ohms.
To solve for vth you need to use the current divider rule:
VTH = 12 [(12)*(68//88)/(68//88 + 100)] = 3.3 volts.
(1)
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