Question

A -15 nC charge is located at the origin.

Part A: What is the strength of the electric field at the position (x,y)=(0cm,5.0cm)?

Part B: What is the strength of the electric field at the position (x,y)=(−5.0cm,−5.0cm)?

Part C: What is the strength of the electric field at the position (x,y)=(−5.0cm,5.0cm)?

Answer 1

Charge, Q = -15 nC = -15 x 10^-9 C

Expression for the electric field at a distance R from a charge Q is given as -

E = k*Q/R^2 [here k is the coulomb's constant having value 9.0 x 10^9 N*m^2/C^2]

Part A -

Here, R = sqrt[0^2 + 5.0^2] = 5.0 cm = 0.05 m

So, E = [(9.0 x 10^9) x (-15 x 10^-9)] / 0.05^2 = -5.40 x 10^4 N/C (Answer)

Part B -

R = sqrt[(-5.0)^2 + (-5.0)^2] = sqrt[50] = 7.07 cm = 0.0707 m

So, E = [(9.0 x 10^9) x (-15 x 10^-9)] / 0.0707^2 = -2.70 x 10^4 N/C (Answer)

Part C -

R = sqrt[(-5.0)^2 + (5.0)^2] = sqrt[50] = 7.07 cm = 0.0707 m

So, E = [(9.0 x 10^9) x (-15 x 10^-9)] / 0.0707^2 = -2.70 x 10^4 N/C (Answer)