10.27: The circuit shown co*w r,0bt jm)nxntains a battery (of emf $V_bat$) with an internal resistance r connected to a rheostat (variable resistor). When the resistance of the rheostat is increased, which of the following statements is true?

  12.39: For the circuit shown, all wi 8uh reskkq(vk6o n:q 6ws8,x5o *fpb+res have no resistance, the battery has a constant internal resistanshnor+q*6vqkkf w8 (p,s 6 k58b xeo:uce of $r = 8.0Ω$ and the two lightbulbs (#1 and #2) are identical, each with resistance R bulb. The variable resistor is initially setto $R = 26.0Ω$ . The switch in the circuit now is closed. To what resistance must the variable resistor be set if bulb #1 is to have the same brightness after the switch is closed as it did with the switch open?