30. THEME FOCUS What happens to the mag netic force as the distance between two magnetic poles decreases? A) It remains constant. B) It decreases. C) It increases. D) It decreases then increases. 31. Which describes the direction of the elec- tric current in AC? A) It is constant. B) It is direct. C) It varies regularly. D) It varies irregularly. . Which is not part of a generator? A) wire coil C) turbine B) magnet D) battery

## Step1<br />For question 30, we need to understand the relationship between the magnetic force and the distance between two magnetic poles. According to the inverse square law, the magnetic force between two magnetic poles is inversely proportional to the square of the distance between them. This means that as the distance between the poles decreases, the magnetic force increases.<br /><br />## Step2<br />For question 31, we need to understand the nature of alternating current (AC). AC is a type of electrical current where the direction of the current changes regularly. This is in contrast to direct current (DC), where the direction of the current remains constant.<br /><br />## Step3<br />For question 32, we need to identify the component that is not part of a generator. A generator typically consists of a wire coil, a turbine, and a magnet. The wire coil is where the current is induced, the turbine is used to spin the coil, and the magnet is used to create the magnetic field. A battery, however, is not a part of a generator. It is a separate device that stores electrical energy.