Which of the following electrical appliances does not utilize the 'magnetic effect of electric current' in its primary working principle?

How does the magnetic field at a distance r from an infinitely long wire change if the current is doubled?

The force on a current-carrying conductor in a magnetic field is maximum when _____.

An electron moves vertically downwards into a magnetic field directed towards the right. According to Fleming's Left-Hand Rule, the direction of the magnetic force acting on the electron will be: