The cross-sectional area of a wire is 1 . 0 × 10 - 7 m 2 and the density of free electrons is 2 . 0 × 10 28 m - 3 . What will be the drift velocity of the free electrons for a current of 3 . 2 A in the wire?

Formula used : I = neAv d , Where I is electric current, n is the no. of electrons, A is the area of cross-section, and V d is the drift velocity of electron. ⇒ v d = I neA = 3 . 2 2 × 10 28 × 1 . 6 × 10 − 19 × 10 − 7 = 1 10 2 = 0 . 01 ms - 1

90 C charge flows for 75 minutes in silver wire of diameter 1 . 0 mm . The free-electron density in the wire is 5 . 8 × 10 28 m - 3 . Find the current and the drift velocity of free electrons in the wire.

Formula used : Q = I . T Where Q is electric charge I is electric current T is time . I = 90 75 × 60 = 1 50 = 0 . 02 A Formula : v d = I neA Where A is area of cross-section. v d = 0 .02 5 .8 × 10 28 × 1 .6 × 10 − 19 × 3 .14 × 10 − 6 2 .74 × 10 − 6 m / s

HARD

12th ICSE

IMPORTANT

Earn 100

Explain resistivity, show its variation with temperature for

(i) conductors (ii) semi-conductors (iii) alloys.

Important Questions on Electric Resistance and Ohm's Law

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 6

Define and write units of specific resistance and specific conductance. Some mass of a metal wire is drawn in two wires in such a way that second one is double in thickness. Compare the resistances.

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NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 7

Show that effective resistance in series combination increases. While that in parallel combination decreases. Two wires of iron and copper of same dimensions are connected in series. The iron wire burns out but the copper wire not even visible glow.Explain.

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 1

A current of

20 μA

flows in a wire for

30

seconds. Find the amount of charge and the number of free electrons transferred through the wire.

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IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 2

A current of $1 A$ is flowing through a conductor. How many electrons pass through any cross-section of the conductor per second ?

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12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 2

A current of

1 A

is flowing through a conductor. How many electrons pass through any cross-section of the conductor in

1.6

second?

EASY

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 3

The cross-sectional area of a wire is

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

and the density of free electrons is

2.0 \times 10^{28} m^{- 3}

. What will be the drift velocity of the free electrons for a current of

3.2 A

in the wire?

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 4

90 C

charge flows for

75

minutes in silver wire of diameter

1.0 mm

. The free-electron density in the wire is

5.8 \times 10^{28} m^{- 3}

. Find the current and the drift velocity of free electrons in the wire.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 5

Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area

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

carrying a current of

1.5 A

. Assume that each copper atom contributes one conduction electron. The density of copper is

9.0 \times 10^{- 3}

m^{- 3}

and its atomic mass is

63.5

. Take Avogadro's number

N = 6.0 \times 10^{23} {mol}^{- 1}

Explain resistivity, show its variation with temperature for (i) conductors (ii) semi-conductors (iii) alloys.

Important Questions on Electric Resistance and Ohm's Law

Learn and Prepare for any exam you want !

Explain resistivity, show its variation with temperature for

(i) conductors (ii) semi-conductors (iii) alloys.