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Circuit Theorems and Conversions - Engineering

Q1:

Referring to the given circuit, the voltage and current for the load resistor, RL, is

A 450 mV, 4.5 mA

B 4.50 V, 45 mA

C 4.50 V, 4.5 mA

D 450 mV, 45 mA

ANS:C - 4.50 V, 4.5 mA

To get the Rth.
Rth = ((R1xR2)/R1+R2) + ((R3xR4)/R3+R4).
Rth = 422 approx.

Use voltage divider of R1 and R2. use voltage divider of R3 and R4. then subtract voltage divider of R1 and R2 to voltage divider of R3 and R4.

=> V12 = Vs( R2/(R2 + R1)).
V12 = 22.6667V.

=> V34 = Vs( R4/(R4 + R3)).
V34 = 16.31 V.

To get the Vth.
Vth = V12 - V34.
Then, Vth = 6.36 V.

To get the Voltage load, use a voltage divider of Vth, Rth and RL.
VL = 6.36( 1000/(1000+422)).
VL = 4.5 V.

To get the current load, use the current divider.
Vth = Ith(Rth).
Here; Ith = 0.01517 A.

So, IL = Ith(Rth/(Rth +RL)).
= 0.01517 (422/(422 + 1000).
Therefore IL = 4.5mA.