Question

What is the magnitude of the electric field at a point midway between a -7.7 uC and a +7.8 C charge 10 cm apart? Assume no other charges are nearby. Express your answer using two significant figures. IP μΑ ? N E = 30860000 С Submit Previous Answers Request Answer X Incorrect; Try Again; 13 attempts remaining Part B What is the direction of the electric field? Pearson Copyright © 2020 Pearson Education Inc. All rights reserved. Terms of Use | Privacy Policy | Permissions Contact Us

Answer 1

A)
q1 = - 7.7 * 10^-6 C
q2 = 7.8 * 10^-6 C
r = 0.05 m, which is the distance from the charges.

Since the electric field from the positive charge is towards the midpoint and the electric field from the negative charge is away from it, the two electric fields can be added,
The electric field at the midpoint,
E = (k * q1) / r² + (k * q2) / r²
Where k = 9.0 * 109 Nm²/C²
E = k / r² [q1 + q2]
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Substituting values,
E = (9 * 10⁹ / (5 * 10^-2)²] * [(7.7 * 10^-6) + (7.8 * 10^-6)]
= 5.6 * 10⁷ N/C

B)
The electric field is directed from positive charge to the negative charge.