# Homework Help: Modelling a Low freq Dipole Using exact and approximate formulation

1. Nov 28, 2012

### mogley76

1. The problem statement, all variables and given/known data
consider s dipole with spacing of 2cm between the two sources. it is radiating a 100hz pure tone, and the magnitude of each source 'A' is given by 1n/M^2.
calculate the pressure as a function of the angle between the reciever and the dipole for a reciever 10 m from the dipole centre, plot graphs of rms vs angle and pressure vs angle using both approximate and exact equations.

2. Relevant equations
exact: p(r)=p1(r1) + p2(r2) = A/r1 e^-j(kr1) - A/r2 e^-j(kr2)

approx: modulus of p(θ,r) ≈ (2AKd *modulus of sin(θ) )/r

3. The attempt at a solution

i plotted these in matlab but there was a small difference between the two plots obtained from the formulations which i cant work out, the exact formulation was slightly bigger than the approximate one. can anyone explain to me please?

Last edited by a moderator: Nov 29, 2012