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In an experiment with potentiometer, the balancing length is $250 cm$ for a cell. When the cell is shunted by a resistance of $7.5 Ω$ , the balancing point is shifted by $25 cm$ . If the cell is shunted by a resistance of $20 Ω$ , the balancing length will be nearly

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Important Questions on Current Electricity

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

An ideal battery of emf

4 V

and resistance

R

are connected in series in the primary circuit of a potentiometer of length

1 m

and resistance

5 Ω .

The value of

R,

to give a potential difference of

5 m V

across

10 c m

of potentiometer wire, is:

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer wire

AB

having length

L

and resistance

12 r

is joined to a cell

D

of emf

ε

and internal resistance

r

. A cell

C

having EMF

ε / 2

and internal resistance

3 r

is connected. The length

AJ

, at which the galvanometer, as shown in the figure, shows no deflection is

Question Image

HARD

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

The length of a potentiometer wire is

1200 c m

and it carries a current of

60 m A

For a cell of

e m f 5 V

and internal resistance of

20 Ω

the null point on it is found to be at

1000 c m

The resistance of whole wire is:

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer wire is

100 cm

long and a constant potential difference is maintained 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 cm

and

10 cm

from the positive end of the wire in the two cases. The ratio of EMF's is :

HARD

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across 52 cm of the potentiometer wire. If the cell is shunted by a resistance of

5 Ω

,a balance is found when the cell is connected across 40 cm of the wire. Find the internal resistance of the cell.

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer wire $P Q$ of $1 m$ length is connected to a standard cell $E_{1}$ . Another cell $E_{2}$ of emf $1.02 V$ is connected with a resistance $r$ and switch $S$ (as shown in figure). With switch $S$ open, the null position is obtained at a distance of $49 cm$ from $Q$ . The potential gradient in the potentiometer wire is :

Question Image

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A B

is a wire of potentiometer with the increase in the value of resistance

R

, the shift in the balance point

J

will be

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

Two wires

A

and

B

of equal lengths are connected in left and right gaps, of meter bridge, respectively. The null point is obtained at

40 cm

from left end. Diameters of the wires

A

and

B

are in the ratio

3 : 1

, the ratio of specific resistance of

A

to that of

B

HARD

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

The balancing length for a cell is

560 c m

in a potentiometer experiment. When an external resistance of

10 Ω

is connected in parallel to the cell, the balancing length changes by

60 c m

. If the internal resistance of the cell is

\frac{n}{10} Ω

, where n is an integer then value of n is ________

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

In the circuit shown, a four-wire potentiometer is made of a

400 c m

long wire, which extends between

A

and

B

. The resistance per unit length of the potentiometer wire is

r = 0.01 Ω / c m .

If an ideal voltmeter is connected as shown with jockey

J

50 c m

from end

A

, the expected reading of the voltmeter will be:
Question Image

HARD

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer wire of length

L

and a resistance

r

are connected in series with a battery of e.m.f.

E_{0}

and a resistance

r_{1}

. An unknown e.m.f.

E

is balanced at a length

l

of the potentiometer wire. The e.m.f.

E

will be given by:

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer

P Q

is set up to compare two resistances, as shown in the figure. The ammeter

A

in the circuit reads

1.0 A

when the two-way key

K_{3}

is open. The balance point is at a length

l_{1} cm

from

P

when the two-way key

K_{3}

is plugged in between

2 and 1

, while the balance point is at a length

l_{2} cm

from

P

when the key

K_{3}

is plugged in between

3 and 1

. The ratio of two resistances

\frac{R_{1}}{R_{2}},

is found to be
Question Image

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer has a uniform wire of length

5 m .

A battery of emf

10 V

and negligible internal resistance is connected between its ends. A secondary cell connected to the circuit gives balancing length at

200 cm

. The emf of the secondary cell is

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

In a potentiometer experiment, the balancing point with a cell is at a length

240 cm

. On shunting the cell with a resistance of

2 Ω

, the balancing length becomes

120 cm

. The internal resistance of the cell is

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

The length of a potentiometer wire is

L .

A cell of e.m.f.

E

is balanced at a length

\frac{L}{5}

from the positive end of the wire. If the length of the wire is increased by

\frac{L}{2}

, at what distance will the same cell give a balance point?

HARD

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

In a potentiometer, a wire of length

10 m

having resistance

50 Ω

is used. A battery of

5 V

and a resistor of

450 Ω

are connected in series to the wire. If an unknown battery of emf

' E'

balances the potentiometer at

450 cm

, then the value of

E

HARD

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

If the balancing length in a potentiometer experiment changes by

10 %

when the cell of unknown emf is shunted by

6 Ω

resistance, then the internal resistance of the cell in

Ω

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of

2.0 V

and a negligible internal resistance. The potentiometer wire itself is

4 m

long. When the resistance,

R,

connected across the given cell, has values of.

(i)

infinity

(i i) 9.5 Ω

The 'balancing lengths, on the potentiometer wire are found to be

3 m

and

2.85 m,

respectively. The value of internal resistance of the cell is:

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

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

EASY

Physics>Electricity and Magnetism>Current Electricity>Potentiometer

A potentiometer wire has length

4 m

and resistance

8 Ω

. The resistance that must be connected in series with the wire and an accumulator of e.m.f.

2V

, so as to get a potential gradient

1 mV

per cm on the wire is :

In an experiment with potentiometer, the balancing length is 250 cm for a cell. When the cell is shunted by a resistance of 7.5 Ω, the balancing point is shifted by 25 cm. If the cell is shunted by a resistance of 20 Ω, the balancing length will be nearly

Important Questions on Current Electricity

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In an experiment with potentiometer, the balancing length is $250 cm$ for a cell. When the cell is shunted by a resistance of $7.5 Ω$ , the balancing point is shifted by $25 cm$ . If the cell is shunted by a resistance of $20 Ω$ , the balancing length will be nearly