If a toroid used bismuth for its core, will the field in the core be (slightly) greater or (slightly) less than when the core is empty?

When rain is accompanied by a thunderstorm, the collected rain water will have a pH value (1)Slightly lower than that of rain water without thunderstorm. (2)Slightly higher than that when the thunderstorm is not there. (3)Uninfluenced by occurrence of thunderstorm. (4)Which depends on the amount of dust in air

A spring of spring constant 'k' is used to suspend a mass 'm' at its free end while the other end of the spring is rigidly fixed. If the mass is slightly depressed and released, then name the motion of the mass.

When a mass is suspended on a metallic wire, the length of the wire increases slightly. Name and state the law that relates to the restoring force developed in the wire and its deformation.

A toroid has a core (non-ferromagnetic) of inner radius 25 cm and outer radius 26 cm, around which 3500 turns of a wire are wound. If the current in the wire is 11 A. What is the magnetic field a. outside the toroid b. inside the core of the toroid, and c. in the empty space surrounded by the toroid.