Question

Calculate the value of the electric field when the filed point is located at 3 c
point charge. The charge of the point charge is 4 nC.
(A) 4000 N/C
(B) 2000 N/C
(C) 3300 N/C
(D) 1000 N/C​

Answer 1

Answer:

B

Explanation:

For point charge

E=V/r

Given 

V=15J/C

E=30N/C

Distance from point charge, r=?

Point charge, q=?

r=V/E=15/30=0.5m

V=4πε0rq

q=4πε0rV

q=9×1091×0.5×15

q=0.83×10−9C

q=0.83nC

Answer 2

The value of the electric field is (A) 4000 N/C.

Given: The distance of field point from point charge = 3 cm

The magnitude of the point charge is =  4 nC.

To Find: The value of the electric field.

Solution:

• Electric field can be considered as an electric property associated with each point in the space where a charge is present in any form. It is the electric force per unit charge.
• The electric field at a point can be calculated using the formula

        E = kq / r²                                               ...(1)

Where k = 1 / ( 4πε0) = 9 × 10^9 N m²/ C², q = charge, r = distance.

Coming to the numerical, we are given;

Magnitude of point charge = 4 nC = 4 × 10^-9 C

The distance from the point charge = 3 cm = 3 × 10^-2 m

Putting respective values in (1), we get;

           E = kq / r²

      ⇒  E = ( 9 × 10^9 × 4 × 10^-9 ) / ( 3 × 10^-2 )²

      ⇒  E = 36 / ( 9 ×10^-4)

      ⇒  E = 4000 N/C

Hence, the value of the electric field is (A) 4000 N/C.

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