10.27: The circuit shown contains a battery (of em1xmz.6jf :k lxf $V_bat$) 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 wires have no resistance, the battf rhvhn1zyfus 7)s v38/25aysyrxq ,b yi:c3)ery has a constant internal res1r5ss: n2 qc/v3 hsxf3i8r) ),ub7 hyfyzy vyaistance 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?