# A Note on Spacetime Black Hole Entropy

Comments: 6 pages, 3 figures

We study the entropy of a black hole in the presence of an external magnetic field. By considering the first order Hamiltonian of an external magnetic field, we derive the entropy in the presence of an external magnetic field. The results show that the entropy of a black hole is dependent on the presence of the external magnetic field. The entropy of a black hole with an external magnetic field is also studied.