Exercise 1

A galvanometer needle deflects full scale for a57.0-?Acurrent.What current will give full-scale deflection if the magnetic field weakens to 0.780 of its original value?Express your answer using three significant figures and include the appropriate units.

Exercise 2

A toroid is a solenoid in the shape of a donut.

R Path 1 Path 2 (a) (b) (a) A toroid or torus. (b) A section of the toroid showing direction of the current for three loops: @ means current toward you, and @ means current away from you