How does jack attempt to take power from Ralph?

Jack shows his power over Piggy from the very first time they meet when he tells Piggy to shut up. Throughout the book Jack continually speaks dismissively to Piggy, telling him that he isn't wanted on the expedition to the mountain, calling him a fat slug during a meeting and continually belittling the fat boy. Piggy is fully aware that Jack hates him and Jack makes this abundantly clear for everyone to see. Refusing to give Piggy any meat and punching him are two further examples of Jack demonstrating his power and physical prowess over the fat and ineffectual Piggy.