(a) sketch mobility as a function of temperature, pointing out the temperature dependences in different regimes. if two different sources of scattering give mobilities of 250cm2/v s and 500cm2/v s, what is the overall mobility? hint: use - . [2+21 (b) consider an experiment where excess electrons are generated in a burst at 0 at z zo in a semiconductor, resulting in a concentration profile given by n(z; t = 0) = δ(z-zo). sketch the shapes of the concentration profile n(z, t) vs z for various times after the initial burst. give reasons for your answer. [2] now consider there is an additional applied uniform electric field eo in the z-direction. sketch the shapes of the concentration profile n(z, t) vs z for various times after the initial burst. describe what happens if, now, a magnetic field is applied in the x-direction. hint: remember the lorentz equation f- q(e +vx b) used for hall measurement. give reasons for your answer in every case.

Amagnetic field "does not" interact with stationary electric charges. so, a.hope my answer you : )

Answer: a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same sign as the  -4.0  µc charge.======electricstatic force between two point charges  is given by    where k is coulomb's constant,  8.99×10⁹  n·m²/c², q₁ and q₂ are the point charges, and r is the distance between the two point charges.assign positive to q₁let q₁ =  6.0 µc, q₂ = -4.0  µc, q₀ represent the charge at the origin, and q₃ represent this new charge to place.the charge at the origin q₀ would experience the following force f₀₁ from q₁, with r = 6.0 m (note that 1  µc = 10⁻⁶ c)    the force from q₂    the force from q₃    the net force on the origin charge, q₀, has to be zero for no electrostatic forcehaving an equation where k and q₀ can be divided out of the equation will allow us to solve for q₃    isolating:     a charge of -1.0  × 10⁻⁴ c must be placed  at x = 26 m.the sign of the charge will be the same as the  -4.0  µc charge