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Question: Answered & Verified by Expert
A $8 \Omega$ resistor is connected to a battery that has an internal resistance of $0.2 \Omega$. If the voltage across the battery (the terminal voltage) is $10 \mathrm{~V}$, then the emf of the battery is
PhysicsCurrent ElectricityAP EAMCETAP EAMCET 2022 (07 Jul Shift 2)
Options:
  • A $10.15 \mathrm{~V}$
  • B $10.20 \mathrm{~V}$
  • C $10.25 \mathrm{~V}$
  • D $9.80 \mathrm{~V}$
Solution:
2326 Upvotes Verified Answer
The correct answer is: $10.25 \mathrm{~V}$
The given situation is shown below


If $I=$ current in circuit then

Where,
$$
\begin{gathered}
E-I r=V \\
I=V / R
\end{gathered}
$$

Here, given,
$$
\begin{aligned}
& R=8 \Omega \\
& r=0.2 \Omega V=10 \mathrm{~V}
\end{aligned}
$$

Hence, circuit current
$$
I=\frac{V}{R}=\frac{10}{8}=\frac{5}{4} \mathrm{~A}
$$

Now, from eq. (i) with values we have,
$$
E=V+I r=10+\frac{5}{4} \times 0.2=10+0.25=10.25 \mathrm{~V}
$$

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