A crossed-field velocity selector has a magnetic field of magnitude 0.03 T. The mass of the electron is 9.10939 × 10−31 kg. What electric field strength is required if 6.5 keV electrons are to pass through undeflected?

E = 4.78*10^6 N/C

Explanation:

In this case you have to take into account that both magnetic force and electric force must be equal

However, you have to know first what is the speed of the electron by using the expression for the kinetic energy (1keV=1000*1.6*10^{-19}J):

by replacing in the expression for the forces you have

HOPE THIS HELPS!!

d₁ = displacement of tern from arctic to antarctic = 11000 miles

d₂ = displacement of tern from antarctic to arctic =   - 11000 miles

d = total displacement for the journey

total displacement for the journey is given as

d = d₁ + d₂

d = 11000 + (-11000)

d = 0 miles

t₁ = time of travel from arctic to antarctic = 3 months = 3 x 30 days = 90 days

t₂ = time of travel from antarctic to arctic = 3 months = 3 x 30 days = 90 days

t = total time of travel

total time of travel is given as

t = t₁ + t₂

t = 90 + 90

t = 180 days

average velocity is given as

average velocity = total displacement/ total time

v = d/t

v = 0/180

v = 0 miles/day