Two planets of equal mass orbit each other while they orbit their star in the counterclockwise direction. What is the direction of the acceleration of the center of mass of the double planet system

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.

wavelength divides in half and speed stays the same.