Two 10-cm-diameter charged rings face each other, 25.0cm apart. both rings are charged to +20.0nc. what is the electric field strength at:
a) the midpoint between the two rings?
b) the center of the left ring?

Part A:

Part B:

Explanation:

Part A:

Formula of Electric Field Strength:

Where:

x is the distance from the ring

R is the radius of the ring

is constant permittivity of free space=8.854*10^-12 farads/meter

Q is the charge

For right Ring E at the midpoint can be calculated as:

x for right plate=25/2=12.5 cm=0.125 m

Radius=R=10/2=5 cm=0.05 m

For Left Ring E at the midpoint can be calculated as:

Since charge on both plates is +ve and same in magnitude, the electric field will be same for both plates.

Electric Field at midpoint:

Both rings have same magnitude but the direction of fields will be opposite as they have same charge on them.

Part B:

At center of left ring:

Due to left ring Electric field at center is zero because x=0.

Due to right ring Electric field at center of left ring:

Now: x=25 cm= o.25 m (To the center of left ring)

Electric Field Strength at center of left ring is same as that of right ring.