Question

A small object A, electrically charged, creates an electric field. At a point P located 0.250 m directly north of A, the field has a value of 40.0 N/C directed to the south. what is the charge of object A?

Answer 1

Concept and reason

Use the concept of electric field produced by a point charge.

Calculate the charge of the object A and magnitude of the total electric field using the expression of electric field strength at a point.

Fundamentals

Electric field strength is the region surrounded all over the charged particle or an object in which another charged particle experiences the force.

The expression for the electric field strength is,

Here, E is the electric field strength, k is the Coulomb’s constant, Q is the charge of the object, and r is the distance from the charged particle to the reference point.

The formula for the electric field strength is,

Rearrange the above equation for as follows:

Substitute 40.0 N/C for E, for k, and 0.250 m for r in .

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Hence, the magnitude of the charge is.

The direction of electric field lines is always from positive to negative. Consider the direction of electric field lines towards south is negative y axis, and the direction of electric field lines towards north is positive y axis. Since the direction of electric field is from north to south that is towards negative y axis.

Hence, sign of the charge on object A is negative.

Therefore, the charge of object A is .

Ans:

The charge of object A is.