Home
Class 12
PHYSICS
A long straigth wire of resistance R, ra...

A long straigth wire of resistance `R`, radius `a` and length `l` carries a constant current `I`.The poynting vector for the wire will be

A

`(IR)/(2pial)`

B

`(IR^(2))/(al)`

C

`(I^(2)R)/(al)`

D

`(I^(2)R)/(2pial)`

Text Solution

Verified by Experts

The correct Answer is:
D
If `V` is the potential difference across the wire, then `E=(V)/(l)=(IR)/(l)` and magnetic field at the surface of wire `B=(mu_(0)I)/(2pia)`. Hence poynting vector, directed radially inwards, is gives by `S=(EB)/(mu_(0))=(IR)/(mu_(0)l)(mu_(0)I)/(2pia)=(I^(2)R)/(2pial)`
Hence the correct answer will be (`4`).
Promotional Banner

Topper's Solved these Questions

  • ELECTRO MAGNETIC WAVES

    NARAYNA|Exercise NCERT based|8 Videos

  • ELECTRO MAGNETIC WAVES

    NARAYNA|Exercise LEVEL- V|4 Videos

  • ELECTRO MAGNETIC WAVES

    NARAYNA|Exercise LEVEL- II (C.W.)|15 Videos

  • ELECTRO MAGNETIC INDUCTION

    NARAYNA|Exercise Level-II (H.W)|23 Videos

  • ELECTROMAGNETIC INDUCTION

    NARAYNA|Exercise ASSERTION & REASON|6 Videos

Similar Questions

Explore conceptually related problems

A long straight wire of cross sectional radius a carries a current I. The return current is carried by an identical wire which is parallel to the first wire. The centre to centre distance between the two wires is d. Find the inductance (L) of a length x of this arrangement. Neglect magnetic flux inside the wires.

Write Ampere's circuital law.A long straight wire of a circular cross section (radius a ) carrying steady current.Current is uniformly distributed in the wire.Calculate magnetic field inside the region (r lt a) in the wire.

Figure shows a long straight wire of circular crosssection (radius a) carrying steady current I. The current I is uniformly distributed across this crosssection. Calculate the magnetic field in the region r lt a and r gt a .

In Fig. there is a conducting loop ABCDEF of resistance lambda per unit length placed near a long straight current-carrying wire. The dimension are shows in the figure. The long wire lies in the plane of the loop. The current in the long wire varies as I = I_(0)(t) . The emf induced in the closed loop is

In Fig. there is a conducting loop ABCDEF of resistance lambda per unit length placed near a long straight current-carrying wire. The dimension are shows in the figure. The long wire lies in the plane of the loop. The current in the long wire varies as I = I_(0)(t) . The heat produced in the loop in time t is

Figure shows a long straight wire of a circular cross-section (radius a) carrying steady current l. The current l is uniformly distributed across this cross-section. Calculate the magnetic field in the region r lt a and r gt a

Two infinitely long straight wires lie in the xy-plane along the lines x =pm R . The wire located at x =+R carries a constant current I_(1) and the wire located at x = -R carries a constant current I_(2) . A circular loop of radius R is suspended with its centre at (0,0, sqrt(3)R) and in a plane parallel to the xy-plane. This loop carries a constant current ? in the clockwise direction as seen from above the loop. The current in the wire is taken to be positive if it is in the +hat J direction. Which of the following statements regarding the magnetic field vec B is (are) true?