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In given figure, an ammeter reads $5 \mathrm{~A}$ and voltmeter reads $40 \mathrm{~V}$. The actual value of resistance $R$ is
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2131 Upvotes
Verified Answer
The correct answer is:
greater than $8 \Omega$
$$
\text { Current in ammeter, } I=5 \mathrm{~A}
$$
We know that, voltmeter has a very high resistance. Hence, current flowing through voltmeter is very low.
$$
\begin{array}{ll}
\therefore & 5=I_1+I_2 \Rightarrow I_1=5-I_2 \\
\text { As, } & I_2>0 \\
\therefore & I_1 < 5 \\
\Rightarrow & \frac{40}{R} < 5 \\
\Rightarrow & 8 < R \Rightarrow R>8 \Omega
\end{array}
$$
\text { Current in ammeter, } I=5 \mathrm{~A}
$$
We know that, voltmeter has a very high resistance. Hence, current flowing through voltmeter is very low.
$$
\begin{array}{ll}
\therefore & 5=I_1+I_2 \Rightarrow I_1=5-I_2 \\
\text { As, } & I_2>0 \\
\therefore & I_1 < 5 \\
\Rightarrow & \frac{40}{R} < 5 \\
\Rightarrow & 8 < R \Rightarrow R>8 \Omega
\end{array}
$$
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