B M Sharma Solutions for Chapter: Electrical Measuring Instruments, Exercise 1: Concept application Excercise

A moving coil galvanometer of resistance $20 \mathrm{\Omega }$ gives a full-scale deflection when a current of $1 \mathrm{m}\mathrm{A}$ is passed through it. It is to be converted into an ammeter reading $20 \mathrm{A}$ on a full scale. But the shunt of $0.005 \mathrm{\Omega }$, only is available. What resistance should be connected in series with the galvanometer coil?

In the circuit in figure ammeter and voltmeter are ideal If $E=4 V,R=9 \mathrm{\Omega }$ and $r=1 \mathrm{\Omega }$, find the readings of ammeter and voltmeter.

Resistances $R_1$and $R_2$ each $60 \mathrm{\Omega }$ are connected in series. The potential difference between points $A$ and $B$ is $120 \mathrm{V}$. Find the reading of the voltmeter connected between points $C$ and $D$ if its resistance $R_v=120 \mathrm{\Omega }$.

A cell of emf $3.4 \mathrm{V}$ and internal resistance $3 \mathrm{\Omega }$ is connected to an ammeter having resistance $2 \mathrm{\Omega }$ and to an external resistance of $100 \mathrm{\Omega }$. When a voltmeter is connected across the $100 \mathrm{\Omega }$ resistance, the ammeter reading is $0.04 \mathrm{A}$. Find the voltage reading by the voltmeter and its resistance. Had the voltmeter been an ideal one what would have been its reading?

A milliammeter of range $10 \mathrm{m}\mathrm{A}$ and resistance $9 \mathrm{\Omega }$ is joined in a circuit as shown. The meter gives full-scale deflection for current $I$ when $A$ and $B$ are used as its terminals, i.e., current enters at $A$ and leaves at $B$ ( $C$ is left isolated). Find the value of $I$.

In the circuit, a voltmeter reads $32 \mathrm{V}$, when it is connected across $400 \mathrm{\Omega }$ resistance. Calculate what the same voltmeter will read when it is connected across the $300 \mathrm{\Omega }$ resistance?

A galvanometer (coil resistance $99 \mathrm{\Omega }$) is converted into an ammeter using a shunt of $1 \mathrm{\Omega }$ and connected as shown in the figure $\left(\mathrm{a}\right)$. The ammeter reads $3 \mathrm{A}$. The same galvanometer is converted into a voltmeter by connecting a resistance of $101 \mathrm{\Omega }$ in series. This voltmeter is connected as shown in the figure $\left(\mathrm{b}\right)$. Its reading is found to be $\frac{4}{5}$ of the full-scale reading. Find

$\left(\mathrm{a}\right)$ The internal resistance $r$ of the cell.

$\left(\mathrm{b}\right)$ Range of the ammeter and voltmeter.

$\left(\mathrm{c}\right)$ Full-scale deflection current of the galvanometer.

A battery of emf $1.4 \mathrm{V}$ and internal resistance $2 \mathrm{\Omega }$ is connected to a resistor of $100 \mathrm{\Omega }$ resistance through an ammeter. The resistance of the ammeter is $\frac{4}{3} \mathrm{\Omega }$. A voltmeter has also been connected to find the potential difference across the resistor.

$\left(\mathrm{a}\right)$ The ammeter reads $0.02 \mathrm{A}$. What is the resistance of the voltmeter?