A teacher has information power because of the teacher's access to more information than the students. One positive effect from information power is the person with power can educate everyone else. One negative is the teacher might teach personal opinions inappropriately.
Expert power based on skill, or knowledge on a subject. Positive effect people get the best and most accurate information from someone with expert power. Negative effect someone with expert power could take advantage of someone by providing them with unfinished or misleading information
Connection power is based on who the leader knows. Positive effect connection can help people obtain important things like a job recommendation. Negative effect it can lead to someone getting something they are not deserving of or unqualified to have.