Question

Two batteries of different e.m.f.'s and intemal resistance connected in series with each other and with an external load resistor. The current is $3.0 \,A$. When the polarity of one battery is reversed, the current becomes $1.0\, A$. The ratio of the e.m.f.'s of the two batteries is

• A. 2.5
• B. 2
• C. 1.5
• D. 1

Answer 1

Answer: (B)

$3=\frac{E_{1}+E_{2}}{R+r_{1}+r_{2}}$
$1=\frac{E_{1}-E_{2}}{R+r_{1}+r_{2}}$
$3=\frac{E_{1}+E_{2}}{E_{1}-E_{2}}$
$2=\frac{E_{1}}{E_{2}}$