Ishani clicks "reset" to restore the simulation to its original configuration. Now she runs the simulation several times for the charging capacitor circuit, varying R and C, and she and John pay attention to the graphs of the charge on the capacitor and current through the resistor. John makes several statements characterizing what they observe. Which are correct

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.