电磁感应
1)E=△φ/△t =a²Bsin(120-90)/t = (1/2)a²B/t 2)ω=2π/3t ==>v=wa =2πa/3t E' =BLvsin30 =(1/2)=πa²B/3t 3)Q=It =Et/R =(1/2)a²B/R