SSE JE Electrical Engineering 10 Dec 2020 Papers

Finding ${\mathrm{R}}_{\mathrm{th}}$ :
By replacing all the sources present in the network with their internal impedances, the given circuit reduces to as shown below and further performs series and parallel resistors operations to reduce the circuit. ${\mathrm{R}}_{\mathrm{th}}=20\mathrm{\Omega }$
Finding ${\mathrm{V}}_{\mathrm{th}}$ : Since the 15 Ω resistor is open-circuited no current will flow through it and the voltage across the terminals AB is the same as that of the voltage across the terminals CD it can calculate by using the voltage division rule as shown ${\mathrm{V}}_{\mathrm{th}}={\mathrm{V}}_{\mathrm{DC}}=100\times \left(\frac{10}{10+10}\right)$
${\mathrm{V}}_{\mathrm{th}}=50\mathrm{V}$
∴ Thevenin's Equivalent circuit is given as