Question 572: Current Electricity

Question

An ammeter of resistance $20 \Omega$ gives full scale deflection, when $1 \mathrm{~mA}$ current flows through it. What is the maximum current that can be measured by connecting 4 resistors each of $16 \Omega$ in parallel with the ammeter?

Accepted Answer

Given, $G=20 \Omega$ and $I_g=1 \mathrm{~mA}=1 	imes 10^{-3} \mathrm{~A}$
The equivalent resistance of 4 resistors of $16 \Omega$ each, connected in parallel is
$R_{	ext {eq }}=\frac{R}{n}=\frac{16}{4}=4 \Omega$
The circuit diagram of an ammeter is
So, the maximum current that can be measured,
$I=\frac{I_g G+I_g R_{\mathrm{eq}}}{R_{\mathrm{eq}}}=\frac{I_g\left(G+R_{\mathrm{eq}}ight)}{R_{\mathrm{eq}}}$
$\begin{aligned}
& =\frac{1 	imes 10^{-3}(20+4)}{4} \
& =6 	imes 10^{-3} \mathrm{~A} 	ext { or } 6 \mathrm{~mA}
\end{aligned}$

Answer

6 mA

Answer

4 mA

Answer

8 mA

Answer

2 mA

Current Electricity

An ammeter of resistance 20 \Omega gives full scale deflection, when 1 \mathrm{~mA} current flows through it. What is the maximum current that can be measured by connecting 4 resistors each of 16 \Omega in parallel with the ammeter?

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