A piece of copper and another of germanium are cooled from room temperature to 80 K . The resistance of...

copper decreases and germanium increases

copper increases ∧ germanium decreases

Copper and Silicon are cooled from 300 K to 60 K . The specific resistance

decreases in copper but increases in silicon

increases in copper but decreases in silicon

Constantan wire is used in making standard resistances because its

temperature coefficient of resistance is negligible

The drift velocity of electrons in a conducting medium is due to

motion of conduction electrons due to electric field E →

motion of conduction electrons due to random collisions

repulsion to the conduction electrons due to inner electrons of ions

collisions of conduction electrons with each other

E M B I B E

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 18

EASY

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IMPORTANT

Earn 100

Current flowing through a circuit is shown in the figure then the resistance of the circuit is

62.5% studentsanswered this correctly

Important Questions on Current Electricity

EASY

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 19

Which one of the following devices is non-ohmic?

EASY

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 20

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

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 21

A copper wire of length

1 m

and uniform cross-sectional area

5 \times 10^{- 7} m^{2}

carries a current of

1 A .

Assuming that there are

8 \times 10^{28}

free electrons per

m^{3}

in copper, how long will an electron take to drift from one end of the wire to the other?

EASY

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 22

Drift velocity of electrons in a wire of a certain length and the circular cross-section is,

V_{d .}

. The potential difference across the wire and the wire length is doubled but, the radius of the cross-section is halved. What is the new drift speed?

EASY

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 23

A resistor connected to a battery is heated due to the current in the circuit. Which of the following quantities do not change, assuming the potential difference across the resistor is constant?

EASY

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 24

Assertion :- Resistivity of metals decreases with decrease in temperature but have some finite value as the temperature approaches absolute zero.

Reason :- The residual resistivity near absolute zero is caused primarily by the collision of electrons with impurities and imperfections in the metal.

EASY

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 25

If a wire is stretched to make it $0.2 %$ longer, its resistance will be

EASY

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IMPORTANT

Physics Crash Course NDA & NA EE>Chapter 18 - Current Electricity>Exercise 1>Q 26

The conductivity of a conductor decreases with temperature because, on heating: