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Reflection is one of the main reasons. Reflection is defined as : [Zs-Zl]/[Zs+Zl]
Here Zs is the source impedance and Zl is the load impedance. When they are same, the numerator in the above equation is zero and that ensure that there is no reflection of transferred energy back to the source and entire energy is transferred to the load.
When Zs and Zl are not equal, reflection and hence power transferred to the load vary depending on the difference between the two impedance values.
The subject is a source of confusion for many people. It is true that, when the source impedance (Zs) is fixed, maximum power transfer occurs when the load impedance (Zl) is equal to the source impedance. However, the reverse is not true.
One common misconception is that the source impedance has to be matched to the load impedance for max power transfer. This is not true. If the load impedance is already fixed, then max power transfer occurs when the source impedance is as low as possible.
Maximum power transfer occur when load impedance is conjugate with the source impedance not the equal one. The reactive part or imaginary part should be cancelled, remain only the equal real part.
Reflection is one of the main reasons. Reflection is defined as : [Zs-Zl]/[Zs+Zl]
Here Zs is the source impedance and Zl is the load impedance. When they are same, the numerator in the above equation is zero and that ensure that there is no reflection of transferred energy back to the source and entire energy is transferred to the load.
When Zs and Zl are not equal, reflection and hence power transferred to the load vary depending on the difference between the two impedance values.
By reflection, do you mean the energy transferring back to source due to inductance and capactance? Could you please say how that relation [Zs-Zl]/[Zs+Zl] was achieved?
To answer your question in the simplest way:
Power is the product of voltage and current.
When the load impedance is larger then the source impedance, current transfer will be low due to large impedance of load.
When the load impedance is higher than the source impedance, voltage transfer will be low due to voltage loss across the internal source impedance.
Maximum power transfer is a comprimise between these two possibilities.
You could use calculus ( min / max technique ) to verify that the maximum will occur when load impedance and source impedance are equal.
In the above figure, I take Rs is variable and R(load) = 3ohms and Vs=20V then what is the value of Rs?
I want to give options also
options: A) 1 ohm B) 2 ohms C) 3 ohms D) 4 ohms
By reflection, do you mean the energy transferring back to source due to inductance and capactance? Could you please say how that relation [Zs-Zl]/[Zs+Zl] was achieved?
Reflection is the phenomenon that occurs in Electrical/Optical signals when they change the medium of transmission. In this case when an electrical signal changes its medium from an impedance ZS to another medium of impedance ZL, some part of the energy will reflect back into the source medium. There by complete power will not be transferred to the load medium ZL. And both terms ZS and ZL will have inductance and Capacitance parameters in them.
In the above figure, I take Rs is variable and R(load) = 3ohms and Vs=20V then what is the value of Rs?
I want to give options also
options: A) 1 ohm B) 2 ohms C) 3 ohms D) 4 ohms
Your question is not an application of the Maximum Power Transfer Theorum. Maximum power will be delivered to the load when Rs=0 ohms.
An increase in Rs will cause a decrease in current and a decrease in load voltage. Hence load power will decrease.
The Maximum Power Transfer Theorum applies when the load resistance is matched to the fixed internal resistance of the voltage source.
Now, when load resistance increases, current still decrease but load voltage increases. At Rl=0, the load voltage and hence load power is zero.
At Rl=infinity, the load current and hence load power is zero.
In general, Pl = (Vs^2 * Rl)/(Rl + Rs)^2 for the given circuit.
As you can see, if Rl and Vs are held constant then Pl is a maximum when Rs is zero since Rs is only in the denominator.
However, Rl is a different story since it exists in both numerator and denominator.
If you differentiate this equation with respect to Rl and solve for d (Pl) / d (Rl) = 0 the solution for Rl>0 should be Rl=Rs
In the above figure, I take Rs is variable and R(load) = 3ohms and Vs=20V then what is the value of Rs?
I want to give options also
options: A) 1 ohm B) 2 ohms C) 3 ohms D) 4 ohms
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