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 45

MEDIUM

NEET

IMPORTANT

Earn 100

The velocity of an electron at point $A$ is $V_{0}$ , where the cross-sectional area is $a$ . The velocity of the electron at the end of contraction at point $B$ , where the cross-sectional area is $2 a$ , is $V_{1}$ . Find the correct option.

16.67% studentsanswered this correctly

Important Questions on Current Electricity

EASY

NEET

IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 46

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

NEET

IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 47

Identify the correct variation of drift velocity

(v_{d})

with electric field strength

(E) :

EASY

NEET

IMPORTANT

Physics Crash Course NEET>Chapter 13 - Current Electricity>Level 1>Q 48

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?

MEDIUM

NEET

IMPORTANT

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

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?

EASY

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?

EASY

NEET

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.

EASY

NEET

IMPORTANT

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

There are