4. A beam of electrons is accelerated through a potential difference of 9.0 kV before entering a velocity selector. If the B-field of the velocity selector is perpendicular to the velocity and has a value of 0.03 T, what value of the E-field is required (in the magnetic field region) if the particles are to be undeflected?

The required electric field is 1.68 x 10⁶ N/C

Explanation:

Given;

Magnitude of the induced e.m.f = 9.0 kV = 9,000 V

Magnetic field strength is given, B = 0.03 T

mass of electron = 9.11 x 10⁻³¹ kg

charge of electron, q = 1.602 x 10⁻¹⁹ C

Electric field strength = ?

qE = qvB

E = vB

Where;

v is the velocity of the electron

K.E = ¹/₂ × mv² = qV

v² = 2qV/m

E = vB

E = 5.6 x 10⁷ x 0.03 = 1.68 x 10⁶ N/C

The required electric field is 1.68 x 10⁶ N/C

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia