A 50V voltage source is connected to two parallel branches. The top branch has two 10 ohm resistors in series. The bottom branch has an 8 ohm resistor and an unknown resistor R in series. The power di

The circuit consists of a 50V voltage source connected to two parallel branches.

• The top branch contains two $10 \, \Omega$ resistors in series.
• The bottom branch contains an $8 \, \Omega$ resistor and an unknown resistor $R$ in series. The problem states that the power dissipated in the $10 \, \Omega$ resistor is $90 \, \text{W}$.

Let $I_1$ be the current flowing through the top branch. Since the two $10 \, \Omega$ resistors are in series, the same current $I_1$ flows through both of them