How Do You Calculate the Internal Resistance of a Thevenin Voltage Source?

AI Thread Summary
To calculate the internal resistance of a Thevenin voltage source, the open circuit voltage is given as 12 volts, and the voltage across a 100-ohm load is 11.2 volts. The missing voltage of 0.8 volts indicates that internal resistance affects the output. The initial calculation for current is 120 mA, leading to an internal resistance of approximately 6.66 ohms using the formula 0.8 volts divided by 120 mA. The voltage divider equation can also be applied to confirm this, utilizing the known voltages and resistances in the circuit.
bengaltiger14
Messages
135
Reaction score
0

Homework Statement


A real voltage source is of the Thevenin Type. The open circuit voltage of the source is 12 volts. If a 100 ohm load is added to the circuit, the voltage at the same terminals is 11.2 volts. What is the internal resistance of the source.


The Attempt at a Solution




I found the total current in the circuit to be 12/100 = 120mA

If there is .8 volts missing, the internal resistance should be: .8/120mA?
 
Physics news on Phys.org
When they say "real voltage source", that means that you should not ignore the built-in output resistance of the source. So the total current will not be 12V/100 Ohms... you need to include the Rout in that equation as well...
 
I need to find the internal resistance before I can include it in the equation right? After doing .8/120mA=6.66 Ohms. The new total current could be 12V/(100 + 6.66)
 
I'm not sure if that's right, but try it this way -- use the voltage divider equation, since you know the voltage source is 12V, and the divided down voltage across Rout and 100 Ohms is 11.2V...
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Determine the Thevenin equivalent circuit
Replies
2
Views
2K
Connecting a number of EMF sources in a circle to form a circuit
Replies
9
Views
1K
Current through an inductor as a function of time
Replies
10
Views
380
Current through a circuit when the key is open
Replies
42
Views
5K
Understanding Short Circuit Current Paths in Electrical Circuits
Replies
4
Views
2K
Parallel circuit with internal resistance
Replies
6
Views
2K
Mechanisms Involved When Charging a Battery
Replies
10
Views
1K
How to solve for EMF and internal resistance in a circuit?
Replies
8
Views
3K
How Do You Calculate Thevenin Equivalent Circuit Without a Load Resistor?
Replies
3
Views
2K
A circuit involving two non-linear resistances (incandescent lamps)
Replies
14
Views
2K

Hot Threads

Recent Insights

Back
Top