A metal wire of specific resistance 64 × 10 − 8 Ωm and length 1.98 m has a resistance of 7 Ω . Find its radius.

Given that, Specific resistance of the wire is 64 × 10 − 8 Ω m length of the wire is 1.98 m resistance of the metal wire is 7 Ω Expression for resistance of a metal wire is, R = ρ l A Let’s assume radius of the copper wire is r As R = ρ l A = ρ l π r 2 ∴ r 2 = ρ l π R = 64 × 10 − 8 × 1.98 × 7 22 × 7 = 5.76 × 10 − 8 m 2 or r = 2.4 × 10 − 4 m

Calculate the resistance of a 2 m long nichrome wire of radius 0 . 321 mm . Resistivity of nichrome is 15 × 10 − 6 Ωm . If a potential difference of 10 V is applied across this wire, what will be the current in the wire?

Given that, Resistivity of nichrome is 15 × 10 − 6 Ωm Length of the nichrome wire is, l = 2 m Radius of the nichrome wire is, r = 0.321 mm Expression for resistance of the nichrome wire is R = ρ l A = ρ l π r 2 R = 15 × 10 − 6 × 2 π × 0.321 2 = 9.26 Ω According to Ohm’s law, relation between current and voltage is V = I × R Amount of current is I = V R I = 10 9.26 A = 1.08 A

E M B I B E

New Simplified Physics (Vol 1) For Class 12>Chapter 3 - Current Electricity>Problems For Practice>Q 7

EASY

12th CBSE

IMPORTANT

Earn 100

In a hydrogen discharge tube, the number of protons drifting across a cross-section per second is $1.1 \times 10^{18}$ , while the number of electrons drifting in the opposite direction across another cross-section is $3.1 \times 10^{18}$ per second. Find the current flowing in the tube.

Important Questions on Current Electricity

EASY

12th CBSE

IMPORTANT

New Simplified Physics (Vol 1) For Class 12>Chapter 3 - Current Electricity>Problems For Practice>Q 1

A voltage of

30 V

is applied across a color-coded carbon resistor with first, second and third rings of blue, black and yellow colors. What is the current flowing through the resistor?