Question

When a battery sends current through a resistance $R_{1}$ for time $t$, the heat produced in the resistor is $Q .$ When the same battery sends current through another resistance $R _{2}$ for time $t$, the heat produced in $R _{2}$ is again $Q$. Determine the internal resistance of battery:

• A. $r = R _{1} R _{2}$
• B. $r =\frac{ R _{1}}{ R _{2}}$
• C. $r =\sqrt{ R _{1} R _{2}}$
• D. $R _{1}=\frac{ R _{2}}{ r }$

Answer 1

Answer: (C)

A cell of given EMF & internal resistance gives same power for two diff. resistances
$R _{1} \&$ $R _{2}$ if $R _{1} R _{2}= r ^{2}$