1-Earth carries a net charge of -4.1 105 C. The force due to this charge is the

Question

1-Earth carries a net charge of -4.1 105 C. The force due to this charge is the same as if it were concentrated at Earth's center. How much charge would you have to place on a 9.0 g mass in order for the electrical and gravitational forces on it to balance?

2-An electron placed in an electric field experiences an electric force of 5.3 10-10 N. What is the field strength?

3-A 68 nC charge experiences a 140 mN force in a certain electric field.
A- Find the field strength that a 43 µC charge would experience in the same field
B- Find the force on the 43 µC charge.

4-What is the line charge density on a long wire if the electric field 44 cm from the wire has magnitude 220 kN/C and points toward the wire?

5-How strong an electric field is needed to accelerate electrons in a TV tube from rest to one-fifth the speed of light in a distance of 5.0 cm?

Explanation / Answer

1) Q = -4.1*105 C. m = 9.0 g, find q

mass of earth = M

GMm/r2 = k|Q|q/r2

q = GMm/(k|Q|) = 9.73*10-4 C

2) electron charge = e, f = 5.3*10-10 N.

the field strength E = f/e = 3.3*109 N/C

3) q = 68 nC, f = 140 mN,
A- the field strength E = f/q = 2.06 mN/nC
B- the force on Q = 43 µC is E*Q = 88.5 N

4) r = 44 cm, E = 220 kN/C, find

E = /(2r0)

= 2r0E = 5.38*10-6 C/m

negative charge

5) find E

v = 3.0*108 /5 = 6.0*107 m/s, d = 5.0 cm

a = v2/(2d) = F/m = eE/m

so E = mv2/(2ed) = 2.05*105 N/C

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