Answer:
a) # _electron = 31 10¹³ electrons, b) E = 9.1 10⁻¹² N / C , c) P = 7.22 10⁻¹⁶ J
Explanation:
In this exercise we must examine the movement of electrons in an electric field.
a) they ask us for the number of electrons.
The electric current is
i = q / t
q = i t
let's calculate
q = 50 10⁻⁶ 1
q = 50 10⁻⁶ C
For this we can use a rule of direct proportions, if the charge of an electron is 1.6 10⁻¹⁹ C, the number of electrons for the charge of 50 10⁻⁶ C
#_electron = 50 10⁻⁶ C 1 / 1.6 10⁻¹⁹ C
# _electron = 31.25 10¹³ electrons
b) For this part we use kinematics to find the acceleration
v² = v₀² + 2 a x
electrons start from rest, so vo = 0
a = v² / 2x
let's calculate
a = 4²/2 5
a = 1.6 m / s²
Having the acceleration we can use Newton's second law where the force is electric
F = ma
e E = m a
E = m / e a
let's calculate
e = 9.1 10⁻³¹ / 1.6 10⁻¹⁹ 1.6
E = 9.1 10⁻¹² N / C
c) what the power on the screen
for this we must add the kinetic energy of all the electrons in the given time
P = # _electron Km / y
P = # _electron (½ m v²) / t
let's calculate
P = 31 10 13 (½ 9.1 10-31 1.6²) / 1
P = 7.22 10⁻¹⁶ J
