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 $P_1$. When the same batteries are connected in parallel across $R$, the rate of heat produced is $P_2$. If $\mathrm{P}_1=2.25 \mathrm{P}_2$, then the value of R is

• A

  $2 \Omega$
• Correct answer
  B

  $4 \Omega$
• C

  $10 \Omega$
• D

  $12 \Omega$

Hence, the correct answer is option: 'B'.