10.27: The circuit shown conta0su-lact jdu7tz;s( 8 vllh 8j-t *y/rins 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 wires have no resistance, t e, tg e2(;afn)i-vmmxhe battery has a constant internal a(mmv2e-gne; x)it , fresistance 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?