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Electric Current and Current Density

A capacitor of 10 {F} has a potential difference of 40 {~V} a

Question

Medium

Solving time: 3 mins

A capacitor of $10 μ F$ has a potential difference of $40 V$ across it. If it is discharged in $0.2 s$ , the average current during discharge is

2 mA

4 mA

1 mA

0.5 mA

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Book:

Master Resource Book in JEE Main Physics (Arihant)

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A capacitor of

10 μ F

has a potential difference of

40 V

across it. If it is discharged in

0.2 s

, the average current during discharge is

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Text solutionVerified

Current

i = \frac{q}{t} = \frac{C V}{t} = \frac{( 10 \times 1 0 ^{- 6} ) \times 40}{0.2} = 2 \times 1 0^{- 3} A = 2 mA

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Practice questions from Master Resource Book in JEE Main Physics (Arihant)

Question 1

Medium

The circuit shown here is used to compare the emf of two cells

E_{1}

and

E_{2} (E_{1} > E_{2})

. The null point is at

C

when the galvanometer is connected to

E_{1}

. When the galvanometer is connected to

E_{2}

, the null point will be

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to the right of $C$
at $C$ itself
none where on $A B$

Topic:

Current Electricity

Book:

Master Resource Book in JEE Main Physics (Arihant)

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Question 2

Medium

Six equal resistances each of

4Ω

are connected to form a figure. The resistance between two corners

A

and

B

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$4/3Ω$
$12Ω$
$2Ω$

Topic:

Current Electricity

Book:

Master Resource Book in JEE Main Physics (Arihant)

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Question 3

Medium

Passage I According to modern view, a metal consists of a lattice of fixed positively charged ions in which billions and billions of free electrons are moving randomly at speed, which at room temperature in accordance with kinetic theory of gases is given by

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, may be of the order of

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or even more. The randomly moving free electrons inside the metal lattice collide with the lattice points and follows as zig-zag path. Consequently, the number of electrons crossing in one direction through a cross-section of metal is exactly equal to the number of free electrons crossing that cross-section in the reverse direction and net electric current is zero. When an external electric field is applied on metal, electrons drift opposite to the field. Thus, random motion of electrons get modified and there is a net transfer of electrons across a cross-section resulting in current. It is mathematically found that drift velocity of electrons is given by

v_{d} = - [\frac{e τ}{m}]

. , where

τ =

mean time between two successive collisions of an electron with lattice points and the resulting current

I = n A_{e v}

where

n =

free electron density in metal and

A

the cross-sectional area. A potential difference of

3.0 V

has been applied across a metal conductor of length

60 cm

. If relaxation period for that metal be taken as

2.5 \times 1 0^{- 14} s

, then the magnitude of drift velocity will be

$2.2 \times 1 0^{- 2} ms^{- 1}$
$2.2 \times 1 0^{- 4} ms^{- 1}$
$1.1 \times 1 0^{- 4} ms^{- 1}$
$1.1 \times 1 0^{- 6} ms^{- 1}$

Topic:

Current Electricity

Book:

Master Resource Book in JEE Main Physics (Arihant)

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Question 4

Medium

In the given circuit shown in figure, it is observed that the current

i

is independent of the value of resistance

R_{6}

. Then, the resistance values must satisfy

$R_{1} R_{2} R_{5} = R_{3} R_{4} R_{6}$
$\frac{1}{R _{5}} + \frac{1}{R _{6}} = \frac{1}{R _{1} + R _{2}} + \frac{1}{R _{3} + R _{4}}$
$R_{1} R_{4} = R_{2} R_{3}$
$R_{1} R_{3} = R_{2} R_{4} = R_{5} R_{6}$

Topic:

Current Electricity

Book:

Master Resource Book in JEE Main Physics (Arihant)

View 5 solutions

Practice more questions from Current Electricity

Question 1

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The length of a conductor is doubled and its radius is halved, its specific resistance is

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Doubled
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Question 2

Easy

A negligibly small current is passed through a wire of length 15 m and uniform cross-section

6.0 \times 1 0^{- 7} m^{2}

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Book:

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Question 3

Medium

A meter bridge is set-up as shown in figure, to determine an unknown resistance

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using a standard

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resistor. The galvanometer shows null point when tapping-key is at

52 cm

mark. The end-corrections are

1 cm

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respectively for the ends

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Exam:

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Question 4

Easy

x g

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. How many gram of

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Practice questions on similar concepts asked by Filo students

Question 1

Determine the currents in each branch of the network shown below. [3] 30. A device '

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Question 2

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4. (a) Calculate the frequency of a photon of energy

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Question 4

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Question Text	A capacitor of $10 μ F$ has a potential difference of $40 V$ across it. If it is discharged in $0.2 s$ , the average current during discharge is
Topic	Current Electricity
Subject	Physics
Class	Class 12
Answer Type	Text solution:1
Upvotes	100