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

E M B I B E

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 49

MEDIUM

NEET

IMPORTANT

Earn 100

A metal, whose temperature coefficient of resistivity is $5 \times 10^{- 4} {{}^{\circ}C}^{- 1}$ , is heated from $100 ° C$ to $1100 ° C$ . By what factor does the mobllity of electrons in the metal change due to this change in temperature?

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Important Questions on Current Electricity

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NEET

IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 50

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?

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IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 51

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.

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Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 52

There are

8.4 \times 10^{22}

free electrons per

{cm}^{3}

in copper. The current in the wire is

0.21 A

(e = 1.6 \times 10^{- 19} C)

. Then the drift velocity of electrons in a copper wire of

1 {mm}^{2}

cross-section, will be:

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Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 53

There is a current of

40 amperes

in a wire of

10^{- 6} m^{2}

area of cross-section. If the number of free electrons per

m^{3}

is

10^{29}

, then the drift velocity will be

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IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 54

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

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IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 55

The number of free electrons per $10 mm$ of ordinary copper wire is about $2 \times 10^{21}$ . The average drift speed of the electrons is $0.25 mm s^{- 1}$ . The current flowing is:-