Electrical Accessories

A moving coil galvanometer on connecting with a high resistance in series is converted into:

The reading on a high resistance voltmeter, when a cell is connected across it, is 2.5 V. When the terminals of the cell are also connected to resistance of  $5 \mathrm{\Omega }$  as shown in the circuit, the voltmeter reading drops to 2.0 V. The internal resistance of the cell is:

Two tangent galvanometers $A$ and $B$ have coils of radii $8 \mathrm{cm}$ and $16 \mathrm{cm}$ respectively and resistance $8 \mathrm{\Omega }$ each. They are connected in parallel with a cell of emf $4 \mathrm{V}$ and negligible internal resistance. The deflections produced in the tangent galvanometers $A$ and $B$ are $30° \text{and} 60°$ respectively. If $A$ has $2$ turns, then the number of turns $B$ must have is

The deflection in galvanometer falls to ${\left(\frac{1}{4}\right)}^{th}$, when it is shunted by $3 \Omega$ . If additional shunt of $\mathrm{2 \Omega }$ is connected in parallel to earlier shunt, the deflection in galvanometer falls to ${\left(\frac{1}{\alpha }\right)}^{th}$ value. Write the value of $2\alpha$.

Discuss the working of plug key.

Resistance $4\mathrm{\Omega }$ and $6\mathrm{\Omega }$ are connected across the left gap and right gap respectively of a meter bridge. when a $2\mathrm{\Omega }$ resistance is connected in series with the $4\mathrm{\Omega }$ resistance in the left gap, the shift in the balance point is

Resistance ${\mathrm{R}}_1$ and ${\mathrm{R}}_2$ are connected respectively in the left gap and right gap of a metere bridge. If the balance point is located at $55\mathrm{cm}$, the ratio of $\raisebox{1ex}{${\mathrm{R}}_2$}\!\left/ \!\raisebox{-1ex}{${\mathrm{R}}_1$}\right.$ is

A resistance of $5\mathrm{\Omega }$ is connected across the gap of a meter bridge and an unknown resistance, greater than $5\mathrm{\Omega }$, is connected across the other gap. When these resistances are interchanged the balance point shifts by $50\mathrm{cm}$. Neglecting any correction, what is the unknown resistance? The length of wire is $150\mathrm{cm}$.

Which error is removed when the known and unknown resistance are interchange in a meter bridge?

Two resistance are connected in two gaps of meter bridge. The balance is $20\mathrm{cm}$ from the zero end. A resistance of $15 \mathrm{ohms}$ is connected in series with the smaller of the two. The null point shifts to $40 \mathrm{cm}$. What is the value of the bigger resistance?

For a four pole, $16$ slot armature with two coil-side/slot having lap connected progressive winding has single turn coils. Then number of commutator segment is?

A $200\mathrm{V}$ d.c machine working at rated spedd. Voltage across the commutating terminals should indeally be_____.

Operation of a d.c. machine will ________.

Commutator action is analogous to ________ in analog electronics.

What is commulator?

A simple slide wire potentiometer is used for measurement of current in the circuit. The voltage drop across a standard resistor of $0.6\mathrm{\Omega }$ is balanced at $60\mathrm{cm}$. The magnitude of current if the standard cell of $4\mathrm{V}$ is balanced at $50\mathrm{cm}$ is_______.

A standard cell of $1.0185 \mathrm{V}$ is used with a slide wire potentiometer. The balance was obtained at $60\mathrm{cm}$. When an unknown $\mathrm{emf}$ was connected, the balance was obtained at $82\mathrm{cm}$. What is the magnitude of unknown $\mathrm{emf}$?

For measurement of potential difference a potentiometer is preferred over voltmeter because-

Two cells of $\mathrm{emf}\text{'}\mathrm{s}$ approximately $5\mathrm{V}$ and $10\mathrm{V}$ are to be accurately compared using a potentiometer of length $400\mathrm{cm}$.This statement satisfies-

In a potentiometer of $5$ wires, the balance point is obtained on the $2\mathrm{nd}$ wire. To shift the balance point to the $4^{\mathrm{th}}$ we should decrease the current of the main circuit.