Which of the following fields that exist in the charge free regions is/are possible electromagnetic fields:
1
P = 60 sin (ωt + 10x) az
2
\(Q = \frac{{10}}{\rho }\cos \left( {\omega t - 2\rho } \right){a_\phi }\)
3
\(R = 3{\rho ^2}\cot \phi {a_\rho } + \frac{1}{\rho }\cos \phi {a_\phi }\)
4
\(S = \frac{1}{r}\sin \theta \sin \left( {\omega t - 6r} \right){a_\theta }\)