Potentiometer

Q.

How is an ammeter connected in a circuit how is a voltmeter connected in a circuit?

Q. A battery of emf $E_0=12\text{V}$ is connected across a $4\text{m}$ long uniform wire having resistance $4\Omega /\text{m}$. The cells of small emfs ${\epsilon }_1=2\text{V}$ and ${\epsilon }_2=4\text{V}$ having internal resistance $2\Omega$ and $6\Omega$ respectively, are connected as shown in the figure. If galvanometer shows no deflection at the point $N$, the distance of point $N$ from the point $A$ is equal to (in $\text{cm}$)

Q.

State whether a voltmeter has high resistance or low resistance. Give reason.

Q. A potentiometer wire 10 m long and having $‘20{\Omega }^{\prime }$ resistance is connected in series with a battery and a resistance $R=2160\Omega$. A Daniel cell of e.m.f 1.08 V is balanced across the P.D of the resistance ‘R’. The e.m.f of thermocouple is balanced across 300 cm of the wire. The e.m.f of thermocouple is

1. 2 mV
2. 4 mV
3. 3 m/V
4. 1 mV

Q. A cell is connected in the secondary circuit of a potentiometer and a balance point is obtained at 84 cm When the cell is shunted by a $5\Omega$ resistor, the balance point changes to 70 cm. If the $5\Omega$ resistor is replaced with $3\Omega$ resistor then the balance point will be at

1. 53 cm
2. 63 cm
3. 42 cm
4. 112 cm

Q.

Where should a voltmeter be placed in a circuit?

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. 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. $0.5\Omega$
3. $1.25\Omega$
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. In an experiment for calibration of voltmeter, a standard cell of emf 1.5V is balanced at 375cm length of potentiometer wire. The potential difference across a resistance in the circuit is balanced at 1.25 m. If a voltmeter is connected across the same resistance, it reads 0.6V. The error in the voltmeter is

1. 0.1V
2. 0.025V
3. 0.235V
4. 0.18V

Q. A potentiometer wire is 100 cm long and a constant p.d. is maintained across it. Two cells A and B are connected in series first and then in opposition. The balance points were obtained at 50 cm and 30 cm. Find the ratio of the e.m.f.s of the cells.

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

Q. Two cells of e.m.f. $E_1$ and $E_2(E_1>E_2)$ are connected as shown in the figure. When a potentiometer is connected between A and B, the balancing length of the potentiometer wire is 300 cm. On connecting the same potentiometer between A and C, the balancing length is 100 cm. The ratio $\frac{E_1}{E_2}$ is

1. 3 : 1
2. 1 : 3
3. 2 : 3
4. 3 : 2

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

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

Q.

How is a voltmeter connected in a circuit?

Q. If a voltmeter draws zero current from the circuit then it is a potentiometer.

1. False
2. True

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. $0.08\text{V}$
4. $0.16\text{V}$

Q. Three identical cells are connected across potentiometer as shown in figure. When switch S is open, null deflection length of potentiometer wire is 250 cm and when S is closed it is 200 cm. Then internal resistance of each cell is(up to two decimal places)

Q. The potentiometer works on the principle that at constant temperature, the resistance of a wire is proportional to its

1. Length
2. Area of cross section
3. Material density
4. None of the above

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

Q. In the following circuit the potential difference between the points B and C is balanced against 40 cm length of potentiometer wire. In order to balance the potential difference between the points C and D, where should jockey be pressed

1. 32 cm
2. 16 cm
3. 8 cm
4. 4 cm

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. $0.08\text{V}$
4. $0.16\text{V}$

Q. A wire has a non-uniform cross-section as shown in figure. A steady current flows through it. The drift speed of electrons at point $\text{P}$ and $\text{Q}$ is $v_P$ and $v_Q$.

1. Data insufficient
2. $v_P=v_Q$
3. $v_P<v_Q$
4. $v_P>v_Q$

Q. In the following figure, the p.d. between the points $M$ and $N$ is balanced at $50\text{cm}$. length. The length in $\text{cm}$, balancing for the potential difference between points $N$ and $C$ will be –

1. $40$
2. $100$
3. $75$
4. $25$

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. 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. A potentiometer has uniform potential gradient across it. Two cells connected in series (i) to support each other and (ii) to oppose each other are balanced over 6 m and 2 m respectively on the potentiometer wire. The emf’s of the cells are in the ratio of

1. 1 : 2
2. 1 : 1
3. 3 : 1
4. 2 : 1

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