10.27: The circuit shown contains a battery (of emftry) q9zng,ee7w7a7r/ti q l)rtg:l 3 $V_bat$) 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 sh9ia77ga, ;a5y snifr yown, all wires have no resistance, the battery has a constant internal resiysfi7 aa9,;rgia7 5ynstance 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?