A very small current is sent through a wire of length 15 m and cross-sectional area 6 . 0 × 10 - 7 m - 2 Its resistance is measured to be 5 . 0 Ω . Find the specific resistance of the experiment. What will be the specific conductance?

Formula used : R = ρ 1 A , σ = 1 / ρ Where R is the resistance A is the area. l is the length σ is the conductivity ρ is the resistivity. ρ = R ⋅ A l = 5 × 6 × 10 − 7 15 = 2 × 10 − 7 Ω m σ = 1 ρ = 1 2 × 10 − 7 = 5 × 10 6 ( Ω m ) - 1 ρ = 2 × 10 − 7 Ωm Conductivity , σ = 5 × 10 − 6 ( Ω m ) - 1

What length of a wire of diameter 0 . 46 mm and specific resistance 50 × 10 - 6 ohm - cm will be required to prepare a coil of 10 ohm ?

Formula used : resistance R = ρ l A Where l is length, A is area, And ρ is resistivity Step 1 Given : R = 10 Ω A = 3 .14 × ( 0 . 23 ) 2 × 10 6 ρ = 50 × 10 − 6 ohm. cm = 50 × 10 − 8 ohm. m Step 2 : l = R ⋅ A ρ l = 10 × 3 .14 × ( 0 .23 ) 2 × 10 − 6 50 × 10 − 8 l = 0 .033231 × 10 + 2 m = 3 .3231 m l = 332 .31 m

E M B I B E

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 8

HARD

12th ICSE

IMPORTANT

Earn 100

Find out the resistivity of a conductor in which a current density of $2.5 A - m^{- 2}$ is found when an electric field of $15 V - m^{- 1}$ is applied it.

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 9

A very small current is sent through a wire of length

15 m

and cross-sectional area

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

Its resistance is measured to be

5.0 Ω

. Find the specific resistance of the experiment. What will be the specific conductance?

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 10

What length of a wire of diameter

0.46 mm

and specific resistance

50 \times 10^{- 6}

ohm - cm

will be required to prepare a coil of

10 ohm

?

MEDIUM

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 11

The specific resistance of Nichrome is

100 μΩ - cm

. What will be the resistance of a Nichrome wire of

5 m

length and

0.01 {cm}^{2}

area of cross-section?

HARD

12th ICSE

IMPORTANT

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

A piece of copper of mass

50 g

is drawn into a wire of length

50 m

. Find the resistance of the wire. The density and the specific resistance of copper are

8.9 \times 10^{3} kg m^{- 3}

and

1.7 \times 10^{- 8} Ω - m

respectively.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 13

A thick wire of

10 Ω

resistance is drawn into a thin wire so that its length becomes three times. Calculate its new resistance.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 14

A wire of resistance

32 Ω

is melted and redrawn into wire of half its original length. Find the resistance of the new wire.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 15

A

1 - kg

piece of copper is drawn into a wire

1 mm

thick and another piece into a wire

2 mm

thick. Compare the resistances of these wires.

HARD

12th ICSE

IMPORTANT

NOOTAN ISC PHYSICS Class 12 Part-1>Chapter 5 - Electric Resistance and Ohm's Law>QUESTIONS>Q 16

Two copper wires $A$ and $B$ of equal masses are taken. The length of $A$ is double the length of $B$ . If the resistance of the wire $B$ . If the resistance of wire A is $160 Ω$ , then calculate the resistance of wire B.