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In a metallic conductor, under the effect of applied electric field, the free electrons of the conductor

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Important Questions on Current Electricity

HARD

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

Suppose the drift velocity

v_{d}

in a material varied with the applied electric field E as

v_{d} \propto \sqrt{E}

. Then

V - I

graph for a wire made of such a material is best given by:

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

An electron of mass

m

and charge

q

is accelerated from rest in electric field

E

. The velocity acquired by the electron in travelling a distance

x

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

The dimensional formula of mobility is _____

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A. The drift velocity of electrons decreases with the increase in the temperature of conductor.
B. The drift velocity is inversely proportional to the area of cross-section of given conductor.
C. The drift velocity does not depend on the applied potential difference to the conductor.
D. The drift velocity of electron is inversely proportional to the length of the conductor.
E. The drift velocity increases with the increase in the temperature of conductor.

Choose the correct answer from the options given below:

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A current of

5 A

passes through a copper conductor (resistivity

= 1.7 \times 10^{- 8} Ω m

) of radius of cross-section

5 m m

. Find the mobility of the charges if their drift velocity is

1.1 \times 10^{- 3} m s^{- 1}

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

Assertion (A): As soon as a source of emf is connected across a conductor, a current immediately starts flowing through it.
Reason (R): Drift speed of the electron is so large that electron travel from one end of the conductor to the other end almost instantaneously.

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A current of

10 A

exists in a wire of cross-sectional area of

5 {mm}^{2}

with a drift velocity of

2 \times 10^{- 3} {m s}^{- 1} .

The number of free electrons in each cubic meter of the wire is

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A current of $2 A$ flows through a wire of cross-sectional area $25.0 {mm}^{2}$ . The number of free electrons in a cubic meter are $2.0 \times 10^{28}$ . The drift velocity of the electrons is _____ $\times 10^{- 6} {ms}^{- 1}$

(given, charge on electron $= 1.6 \times 10^{- 19} C$ ).

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

Though the electron drift velocity is small and electron charge is very small, a conductor can carry an appreciably large current because

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A charged particle having drift velocity of

7.5 \times 10^{- 4} m s^{- 1}

in an electric field of

3 \times 10^{- 10} V m^{- 1}

, has a mobility in

m^{2} V^{- 1} s^{- 1}

of:

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

The drift velocity of electrons for a conductor connected in an electrical circuit is

V_{d}

. The conductor is now replaced by another conductor with same material and same length but double the area of cross-section. The applied voltage remains same. The new drift velocity of electrons will be

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A copper wire with a cross-section area of

2 \times 10^{- 6} m^{2}

has a free electron density equal to

5 \times 10^{22} {cm}^{- 3} .

If this wire carries a current of

16 A

, the drift velocity of the electron is

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

Assertion: The drift velocity of electrons in a metallic wire will decrease, if the temperature of the wire is increased.

Reason: On increasing the temperature, conductivity of metallic wire decreases.

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A potential difference of

5 V

is applied across a conductor of length

0.1 m

. If the electron mobility is

5 \times 10^{- 6} m^{2} v^{- 1} s^{- 1}

then the drift velocity of electron is

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

Drift speed of electrons, when

1.5 A

current flows in a copper wire of cross section

5 {mm}^{2}

v_{d} .

If the electron density in copper is

9 \times 10^{28} m^{- 3}

the value of

v_{d}

mm s^{- 1}

is close to (Take charge of an electron to be

= 1.6 \times 10^{- 19} C

)

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

The number density of free electrons in copper is nearly

8 \times 10^{28} m^{- 3}

. A copper wire has its area of cross-section

= 2 \times 10^{- 6} m^{2}

and is carrying a current of

3.2 A

. The drift speed of the electrons is _____

\times 10^{- 6} m s^{- 1}

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A copper wire of

3 {m m}^{2}

cross sectional area carries a current of

5

ampere. The magnitude of the drift velocity for the electrons in the wire, (Assume copper to be monovalent,

M_{C u} = 63.5 k g / k m o l

and density of copper

= 8920 k g m^{- 3}

)

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

The number of free electrons per

100 mm

of ordinary copper wire is

2 \times 10^{21}

. Average drift speed of electrons is

0.25 mm s^{- 1}

. The current flowing is

HARD

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

When

5 V

potential difference is applied across a wire of length

0.1 m

, the drift speed of electrons is

2.5 \times 10^{- 4} m s^{- 1}

. If the electron density in the wire is

8 \times 10^{28} m^{- 3}

, the resistivity of the material is close to:

EASY

Physics>Electricity and Magnetism>Current Electricity>Drift Velocity, Mobility and Their Relation with Electric Current

A constant current source is connected to a wire. If the wire is stretched to twice its length, then the drift velocity:

In a metallic conductor, under the effect of applied electric field, the free electrons of the conductor

Important Questions on Current Electricity

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