1) The diagram shows an electron beam entering the region between two metal plates in which there are uniform electric and magnetic fields.

If the speed of the electrons in the beam is 6.00 × 105 m s⁻¹, and the strength of the magnetic field is 0.238 mT, what is the magnitude and direction of the electric field that will allow the beam to pass through undeflected?

2) 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.

3) Parallel conductors WXYZ, carrying equal currents, pass vertically through the four corners of a square. In two conductors, the current is flowing into the screen, and in the other two, out of the screen.

What are the directions of the current in order to produce a resultant magnetic field in the direction shown at O, the centre of the square?

4) 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?

5) P and Q are two ions with masses m_P and m_Q respectively. They have the same charge q and the work done on both charges after passing through an applied p.d. of V is qV. Subsequently, P and Q enter a magnetic field B.

The radius of the path of ions P and Q is r_P and r_Q respectively. What is the ratio of r_Q / r_P?