Question

3. a) The distance between two plates in a plate-like capacitor is d. It is con- nected to a power supply providing a potential difference Eo coswt). Find the magnetic field between the plates. (2p) b) Find the Poynting vector (both magnitude and direction on the surface of a long, linear wire with the resistance R and carrying electric current I. What is the physical process balancing the energy flow described by the Poynting vector? (2p)

Answer 1

lets first what write potential as to instead of Co (af same as Epsilon not) AV=Voloswt E = Vof coswt do di = lo ao de dt & B. de - to Cox Vo sin wt x(w) d 2078 B = Mo hox W x vo d x 2T to? 6) DC current has even distribution inside the wire I - J T2 = a CE and I are in same direction ) a is conductivity ris radius of wire 217 (magnetic field of so e = 1 ang2 Now - Mo I B - current carning wire

Pointing vector 3= 1 Ex B - 1 Mo I 2 to 24283 a ( direction perpendicular to Both Electric field and magnetic field) a 1 (Area) 72 2 Length R R (Res (Resistance per unit lengths This vector is pointing into the current carring wire: Poynting theorem is about conservation of Energy Energy dissipated : flow of EM Energy inside the wire.