関連ワード:  what is the value of magnetic field    what is the value of magnetic field of earth    what is the value of magnetic field inside the solenoid    what is the value of magnetic field constant    what is the value of magnetic field at the centre of a circular loop    what is the value of magnetic field at point o    what is the value of magnetic field intensity    what is the value of magnetic field outside a solenoid    what is the importance of magnetic field    what is the importance of magnetic field on earth