You bring a negatively charged rod close to some tiny pieces of plastic. some of the pieces jump up to the rod, but as soon as they make contact, they immediately fly away from the rod. explain.

The negatively charged rod will induce positive charge on the nearby face of the paper and equal negative charge on the opposite side of the paper. The face which is close to the rod will get attracted to the negatively charged rod and as soon as they make contact, the positive charge on the paper will flow to the rod and Since, there is still negative charge on the other side of the paper, which will repel with the negatively charged rod and will fly away.

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.