10.27: The circuit shown coerjad x56yx:x g)/ac(5le/qpntains 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 wire-+;qfg)k15fl rhk 9iv6wbhifs have no resistance, the battery has a consk1 b6f+ -5frh vifq;w)ikg hl9tant internal resistance 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?