A storage battery of EMF 10 V and internal resistance 1 Ω is being charged by a 120 V dc supply using a series resistor of 21 Ω. What is the terminal voltage of the battery during charging?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → V = 15 V
EMF of the Battery, $ε_{battery}=10V$
Internal Resistance of the battery, $r=1Ω$
External voltage supply, $V_{supply}=120V$
Series Resistance ($R_{series}$) = 21Ω
$R_{total}=R_{series}+R_{battery}$
$=21Ω+1Ω=22Ω$
and,
Current (I) = $\frac{V_{supply}-ε_{battery}}{R_{total}}=\frac{120-10}{22}=5A$
$∴V_{terminal}=ε_{battery}+I×r_{battery}$
$=10+5=15V$