Question

# 1, Two charges are placed on the x axis. One of the charges (q1 = +8.09C)...

1, Two charges are placed on the x axis. One of the charges (q1 = +8.09C) is at x1 = +3.00 cm and the other (q2 = -21.5C) is at x2 = +9.00 cm. Find the net electric field (magnitude and direction given as a plus or minus sign) at (a) x = 0 cm and (b) x = +6.00 cm.

2. Two charges, -22 C and +3.5 C, are fixed in place and separated by 3.0 m. (a) At what spot along a line through the charges is the net electric field zero? Give the distance of the spot to the positive charge in meters (m). (Hint: The spot does not necessarily lie between the two charges.) (b) What would be the force on a charge of +14 C placed at this spot?

1 )

q1 = + 8.09 C

x1 = + 3.00 cm = 0.03 m

q2 = - 21.5 C

x2 = +9.00 cm = 0.09 m

a )

at x = +3.00 cm

E = - k q1 / 0.032 + k q2 / 0.092

E = - 9 X 109 ( 8.09 / 0.032 + 21.5 / 0.092 )

E = - 1.047 X 1014 N/C

b )

at x = +6.00 cm

E = k q1 / 0.032 + k q2 / 0.092

E = 9 X 109 ( 8.09 / 0.032 + 21.5 / 0.032 )

E = 2.959 X 1014 N/C

2 )

a )

given

q1 = -22 C = | -22 | = 22 C

q2 = +3.5 C = | + 3.5 | = 3.5 C

d = 3.0

here E1 = E2

kq1 / ( d +x )2 = kq2 / ( x )2

q1 / ( d +x )2 = q2 / ( x )2

x = q22 / q12 + q22

x = d / ( ( q1/ q2 )1/2 + 1 )

x = 3 / ( 22/3.5 )1/2 + 1

x = 0.855 m

at x = 0.855 m the net electric field zero

b )

if the force on a charge of +14 C placed at this spot is also the force is ZERO.

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