Consider two uniformly charged parallel plates as shown in the figure. The magni

Question

Consider two uniformly charged parallel plates as shown in the figure. The magnitudes of the charges are equal. Select True or False for the following státements Torn ae Fatse for tre ablowing est ateralent slates as shown in the figure. The magnitudes of the charges are equal. Select If the plates are oppositely charged, there is no electric field at c. If both plates are negatively charged, the electric field at a points towards the top of the page a If both plates are positively charged, there is no electric field at b. Submit Answer Tries 0/8 If the plates are 1.0 cm by 1.0 cm squares, and the charges on the plates are +/-1.8 C respectively, what is the magnitude of the electric field at b? Assume that the spaing betweén the plates is much less than 1'cm. Submit Answer Tries 0/8

Explanation / Answer

Electric field due to a plane charged plate is

E = /2o

Here

- is the surface charge density of the plate

o – is the permittivity of free space = 8.854 x 10-12 C2/Nm2

1)

True

When the plates are charged oppositely point c will feel no field because

Net field at C E =repulsive filed by +ve plate - attractive field by –ve plate

E = E+ - E-

Since the electric field due to a plate is E = /2o which is irrespective of the distance

E+ = E-

So E = 0 N/C

2)

False

When both plates are charged negatively,

Net field at A, E = attractive field by –ve plate + attractive field by –ve plate

E = / o N/C

Which is towards the plate towards the bottom of the page

3)

True

When both plates are charged positively, both plates will push the unit positive charge away from themselves and if both have equal charge then the net force will be zero

Net field at B, E = repulsive field by +ve plate - repulsive field by +ve plate

E = 0 N/C

4)

surface area of the plate A = 1 cm x 1 cm = 1 cm2

A = 1 x 10-4 m2

Q = 1.8 x 10-6 C

= Q/A

= 1.8 x 10-6 / 1 x 10-4

= 1.8 x 10-2 C/m2

we found that the electric field at point B is

E = / o

E = 1.8 x 10-2 / 8.854 x 10-12

E = 2.03 x 109 N/C

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