1) An electron moves in a circular orbit in a uniform magnetic field.

Which of the following statements is correct?

2) An electron moves in a circular orbit perpendicular to a uniform magnetic field. A second electron is also moving in a circular orbit in the same magnetic field with twice the radius.

How do the period of revolution and the speed of the second electron compare with those of the first?

3) An electron enters a region where there are uniform electric field and magnetic field of 0.50 T acting at right angles to its horizontal velocity v, as shown in the figure below.

The electron remained undeflected when it enters the region. When the magnetic field is switched off, the electron immediately moved a vertical displacement of 0.15 mm in 1.0 ns.

Calculate the speed of the electron v.

Take the mass of the electron to be 9.11 × 10⁻³¹ kg and the magnitude of its charge to be 1.60 × 10⁻¹⁹ C.

4) An electron enters a region at point O at an angle of 45° to the x-axis as shown. The region contains a magnetic field which is directed into the plane of the page.

An electric field can be applied such that the electron is able to pass through the region undeflected.

Which of the following correctly shows the direction of the electric field from O?

5) When a charged particle is in a region of magnetic field, which of the following is not a necessary condition for the particle to experience a magnetic force?