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Important Questions on Current Electricity

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

A current through a wire depends on time as

i = α_{0} t + β t^{2}

, where

α_{0} = 20 A s^{- 1}

and

β = 8 A s^{- 2}

. Find the charge crossed through a section of the wire in

15 s .

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

Estimate the magnitude of current that passes through a wire, if

0.1 mol

of electrons flow through it in

40 \min

. (Assume Avogadro number

= 6 \times 10^{23}

)

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

The current in a conductor varies with time

t

I = 2 t + 3 t^{2}

, where

I

is in ampere and

t

in seconds. Electric charge flowing through a section of the conductor during

t = 2 \sec

t = 3 \sec

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Electric Current

Three resistors having resistances $r_{1}, r_{2}$ and $r_{3}$ are connected as shown in the given circuit. The ratio $\frac{i_{3}}{i_{1}}$ of currents in terms of resistances used in the circuit is :

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EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

Which of the following acts as a circuit protective device?

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Electric Current

A current of

5 A

is passing through a non-linear magnesium wire of cross-section

0.04 m^{2}

. At every point the direction of current density is at an angle of

60 °

with the unit vector of area of cross-section.
The magnitude of electric field at every point of the conductor is: (resistivity of magnesium

ρ = 44 \times 10^{- 8} Ωm

)

HARD

Physics>Electricity and Magnetism>Current Electricity>Electric Current

A steady current

I

is set up in a wire whose cross-sectional area decreases in the direction of the flow of the current. Then, as we examine the narrowing region,

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

The current density in a cylindrical wire of radius

r = 4.0 mm

1.0 \times 10^{6} A^{2} m^{2}

. The current through the outer portion of the wire between radial distances

\frac{r}{2}

and

r

x π A

; where

x

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

The potential difference between points $A$ and $B$ of adjoining figure is

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EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

A conductor carries a current of

300 mA

. The number of electrons passing through it in

1

minute are ___ .

HARD

Physics>Electricity and Magnetism>Current Electricity>Electric Current

Shown in the figure is a semicircular metallic strip that has thickness $t$ and resistivity $ρ$ . Its inner radius is $R_{1}$ and outer radius is $R_{2}$ . If a voltage $V_{0}$ is applied between its two ends, a current $I$ flows in it. In addition, it is observed that a transverse voltage $Δ V$ develops between its inner and outer surfaces due to purely kinetic effects of moving electrons (ignore any role of the magnetic field due to the current). Then (figure is schematic and not drawn to scale)

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HARD

Physics>Electricity and Magnetism>Current Electricity>Electric Current

An infinite line charge of uniform electric charge density

λ

lies along the axis of an electrically conducting infinite cylindrical shell of radius R. At time t = 0, the space inside the cylinder is filled with a material of permittivity

ε

and electrical conductivity

σ

. The electrical conduction in the material follows Ohm's law. Which one of the following graphs best describes the subsequent variation of the magnitude of current density j(t) at any point in the material?

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

The current density in a cylindrical wire of radius

4 mm

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

. The current through the outer portion of the wire between radial distances

\frac{R}{2}

and

R

is _____

π A

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

A conducting wire of length $l$ , area of cross-section $A$ and electric resistivity $ρ$ is connected between the terminals of a battery. A potential difference $V$ is developed between its ends, causing an electric current. If the length of the wire of the same material is doubled and the area of cross-section is halved, the resultant current would be___

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Electric Current

A circular wire has current density

J = (2 \times 10^{10} \frac{A}{m^{2}}) r^{2}

where

r

is the radial distance, out of the wire radius is

2 mm

. The end-to-end potential applied to the wire is

50 V

. How much energy (in joule) is converted to thermal energy in

100 s

EASY

Physics>Electricity and Magnetism>Current Electricity>Electric Current

Across a metallic conductor of non-uniform cross section a constant potential difference is applied. The quantity which remains constant along the conductor is:

HARD

Physics>Electricity and Magnetism>Current Electricity>Electric Current

In the circuit shown below, the key is pressed at time $t = 0$ . Which of the following statement(s) is(are) true?
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