Potentiometer

Q. In the circuit shown, the switch is shifted from position $1\to 2$ at t = 0. The switch was initially in position 1 since a long time. The graph between charge on capacitor C and time 't' is

1. 
2. 
3. 
4. 

Q. Potentiometer wire is $100\text{cm}$ long and a constant potential difference is maintaned across it. Two cells are connected in series first to support one another and then in opposite direction. The balance points are obtained at $50\text{cm}$ and $10\text{cm}$ from the positive end of the wire in the two cases. The ratio of emf's is:

1. $5:1$
2. $5:4$
3. $3:4$
4. $3:2$

Q. Four plates of equal area A are separated by equal distances $d$ and are arranged as shown in the figure. The equivalent capacity is

1. $\frac{2{\epsilon }_{o}A}{d}$
2. $\frac{3{\epsilon }_{o}A}{d}$
3. $\frac{{\epsilon }_{o}A}{2d}$
4. $\frac{{\epsilon }_{o}A}{d}$

Q.

The resistance $R=\frac{V}{I}$, where $V=(50\pm 2)V$ and $I=(20\pm 0.2)A$. The percentage error in resistance is $x\%$. The value of $x$ to the nearest integer is _________.

Q. $AB$ is a potentiometer wire of length $100\text{cm}$ and its resistance is $10\Omega$. It is connected in series with a resistance $R=40\Omega$ and a battery of emf $2\text{V}$ and negligible internal resistance. If a source of unknown emf $E$ is balanced by $40\text{cm}$ length of the potentiometer wire, then the value of $E$ is

1. $0.8\text{V}$
2. $1.6\text{V}$
3. $0.16\text{V}$
4. $0.08\text{V}$

Q. In an experiment to measure the internal resistance of a cell by a potentiometer, it is found that the balance point is at a length of $2\text{m}$, when the cell is shunted by a $5\Omega$ resistance and at a length of $3\text{m}$, when the cell is shunted by a $10\Omega$ resistance. The internal resistance of the cell is

1. $1.5\Omega$
2. $10\Omega$
3. $1\Omega$
4. $15\Omega$

Q. The balancing length for a cell is 560 cm in a potentiometer experiment. When an external resistance of 10 ohm is connected in parallel to the cell the balancing length changes by 60 cm. The internal resistance of the cell in ohms is

1. 1.6
2. 1.4
3. 1.2
4. 0.12

Q.

What is the temperature coefficient of copper?

Q. A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F, because the method involves

1. a combination of cells, galvanometer and resistances
2. cells
3. potential gradients
4. a condition of no current flow through the galvanometer

Q.

What is effective resistance?

Q.

What are the advantages of a potentiometer?

Q.

In a series LCR circuit, the inductive reactance (X_L) is $10\Omega$and the capacitive reactance (X_C) is $4\Omega$. The resistance (R) in the circuit is $6\Omega$. Find the power factor of the circuit.

1. $\frac{1}{\sqrt{2}}$

2. $\frac{\sqrt{3}}{2}$

3. $\frac{1}{2}$

4. $\frac{1}{2\sqrt{2}}$

Q. 4. In given circuit the potential at point A is

Q. A battery with negligible internal resistance is connected with 10m long wire. A standard cell gets balanced on 600 cm length of this wire. On increasing the length of potentiometer wire by 2m, the null point will be displaced by,

1. 200 cm
2. 120 cm
3. 720 cm
4. 600 cm

Q.

Why do we prefer a potentiometer with a longer bridge wire?

Q.

In the potentiometer circuit shown in figure the internal resistance of the 6 V battery is 1 ohm and the length of the wire AB is 100 cm. When AD = 60 cm the galvanometer shows no deflection. The emf of cell C is (the resistance of wire AB is 2 ohm)

1. 0.7 V
2. 0.8 V
3. 0.9 V
4. 1 V

Q. A daniel cell is balanced on 125 cm length of a potentiometer wire. When the cell is short circuited with a $2\Omega$ resistance, the balancing length obtained is 100 cm. Internal resistance of the cell will be

1. $1.5\Omega$
2. $1.25\Omega$
3. $0.5\Omega$
4. $\frac{4}{5}\Omega$

Q. A 2 volt battery, a $15\Omega$ resistor and a potentiometer of 100 cm length, all are connected in series. If the resistance of potentiometer wire is $5\Omega$, then the potential gradient of the potentiometer wire is

1. 0.005 V/cm
2. 0.05 V/cm
3. 0.02 V/cm
4. 0.2 V/cm

Q.

Why Phosphor Bronze Is Used In Galvanometer?

Q. A wire of radius $r$ has resistance $R$. If it is stretched to a wire of radius $\frac{r}{2},$ then the resistance becomes

1. $2R$
2. $4R$
3. $16R$
4. zero

Q.

Why do we call an ammeter a low resistance galvanometer?

Q. The resistivity of a potentiometer wire is $40\times {10}^{-8}\Omega m$ and its area of cross section is $8\times {10}^{-6}{m}^2$. If 0.2 ampere current is flowing through the wire, the potential gradient will be

1. 1 volt/m
2. ${10}^{-1}$ volt/m
3. ${10}^{-2}$ volt/m
4. $3.2\times {10}^{-2}$ volt/m

Q.

The elastic limit of steel is $8\times {10}^{8}N{m}^{-2}$ and its Young modulus $2\times {10}^{11}N{m}^{-2}$. Find the maximum elongation of a half-metre steel wire that can be given without exceeding the elastic limit.

Q. Potentiometer is an ideal voltmeter because:

1. It has zero resistance
2. It can measure infinite voltage.
3. It can take infinite current from the circuit.
4. It draws zero current from the circuit.

Q.

Consider the potentiometer circuit shown in the figure below. The potentiometer wire is 600 cm long. At what distance from point A should the jockey be placed to get zero deflection in the galvanometer?

1. 320 cm

2. 250 cm

3. 500 cm

4. 430 cm

Q.

How EMF is measured?

Q. The circuit shown here is used to compare the e.m.f.'s of the cells $E_1$ and $E_2(E_1>E_2)$. When the galvanometer is connected to $E_1$, the null point is at $C$. When the galvanometer is connected to $E_2$, the null point will be

1. to the left of $C$
2. to the right of $C$
3. at $C$ itself
4. no where on $AB$

Q.

What is a potential difference of a cell ?

Q. Consider the circuit shown in figure. When switch $S_1$ closed and the other two switches open, the circuit has a time constant $0.05\text{sec}$. When switch $S_2$ closed and the other two switches open, the circuit has a time consatnt $2\text{sec}$. When switch $S_3$ closed an the other two switches open, the circuit oscillates with a period $T$. Find $T(\text{in sec). Take}{\pi }^2=10$

Q. With a certain cell, the balance point is obtained at 0.60 m from one end of the potentiometer. With another cell whose emf differs from that of the first by 0.1 V, the balance point is obtained at 0.55 m. Then, the two emf’s are

1. 1.2 V, 1.1 V
2. 1.2 V, 1.3 V
3. – 1.1 V, – 1.0 V
4. None of the above