<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A magnetic field is a vector field that describes the magnetic influence of electrical currents and magnetized materials . In everyday life, the effects of magnetic fields are most readily encountered with nearby permanent magnets, which pull on magnetic materials (such as iron) and attract or repel other magnets . Magnetic fields surround and are created by magnetized material and by moving electric charges (electric currents) such as those used in electromagnets . Magnetic fields exert forces on nearby moving electrical charges and torques on nearby magnets . In addition, a magnetic field that varies with location exerts a force on magnetic materials . Both the strength and direction of a magnetic field varies with location . As such, it is an example of a vector field . </P> <P> The term' magnetic field' is used for two distinct but closely related fields denoted by the symbols B and H. In the International System of Units, H is measured in units of amperes per meter and B is measured in teslas or newtons per meter per ampere . H and B differ in how they account for magnetization . In a vacuum, B and H are the same aside from units; but in a magnetized material, B / μ 0 (\ displaystyle \ mu _ (0)) and H differ by the magnetization M of the material at that point in the material . </P> <P> Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin . Magnetic fields and electric fields are interrelated, and are both components of the electromagnetic force, one of the four fundamental forces of nature . </P>

What is the si unit for magnetic field strength