EASY

Earn 100

A conductor of variable cross-section is connected across a battery. Let us consider two cross-sections $A$ and $a$ . Let $V$ and $v$ be drift speeds of electrons at those cross-sections respectively then

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Important Questions on Current Electricity

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

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

HARD

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

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:

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

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>Ohm's Law

A circuit to verify Ohm's law uses ammeter and voltmeter in series or parallel connected corrected correctly to the resistor. In the circuit :

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

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>Ohm's Law

When a diode is forward biased, it has a voltage drop of

0.5 V

. the safe limit of current through the diode is

10 mA

. If a battery of emf

1.5 V

is used in the circuit, the value of minimum resistance to be connected in series with the diode so that the current does not exceed the safe limit is :

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

To verify Ohm’s law, a student connects the voltmeter across the battery as shown in the figure. The measured voltage is plotted as a function of the current, and the following graph is obtained:
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V_{o}

is almost zero, identify the correct statement:

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

{kgm}^{2} s^{- 3} A^{- 2}

is the SI unit of

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

In the circuit shown below, a student performing Ohm's law experiment accidentally puts the voltmeter and the ammeter as shown in the circuit below; the reading in the voltmeter will be close to
Question Image

MEDIUM

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

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

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

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:

HARD

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

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>Ohm's Law

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>Ohm's Law

A steady current flows in a metallic conductor of non-uniform cross section. The quantity/quantities that remains/remain constant along the length of the conductor is/are

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

$I - V$ characteristic of a copper wire of length $L$ and area of cross-section $A$ is shown in figure. The slope of the curve becomes

Question Image

HARD

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

A voltmeter having a resistance of

900 Ω

is used to measure the potential difference across a

100 Ω

resistor which is connected to a battery of emf

150 V

and internal resistance

10 Ω .

The percentage of decrease in the potential difference across the

100 Ω

resistor when the voltmeter is connected across it is

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

Find the potential difference between $a$ and $b$ , as shown in the below circuit.

Question Image

EASY

Physics>Electricity and Magnetism>Current Electricity>Ohm's Law

In the figure shown, what is the current (in ampere) drawn from the battery? You are given:
$R_{1} = 15 Ω, R_{2} = 10 Ω, R_{3} = 20 Ω, R_{4} = 5 Ω, R_{5} = 25 Ω, R_{6} = 30 Ω, E = 15 V$
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