Two batteries of different emfs and different internal resistance are connected as shown. The voltage across AB in volts is __________.
When two identical batteries of internal resistance 1 $$\Omega$$ each are connected in series across a resistor R, the rate of heat produced in R is J1. When the same batteries are connected in parallel across R, the rate is J2. If J1 = 2.25 J2, then the value of R in $$\Omega$$ is __________.