Question

Agginment
Two point charges of 20 uc and 80 uc
are placed 18cm apart. Find the position
where the electric field is zero?
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Answer 1

Answer:

6 cm from 20 uC

Explanation:

Since both the charges are positive

1) for a point between them the fields will be opposite.

So the point of interest must lie between the two charges.

Please refer the attachment.

also note that if the two charges are of opposite nature then the point will lie closer to the charge with lower magnitude on the other side ( not between them)

Hope it helps you!!!

Answer 2

Answer:

The electric field is zero at 6 cm from 20 micro coulomb charge.

Explanation:

• First point charge, q₁ = $20\times10^{-6}$
• Second point charge, q₂ = $80\times10^{-6}$
• Distance d = 18 cm

Let x cm from 20 micro coulomb electric field would be zero.

According to the formula,

• The electric field from a point charge 20 micro coulomb at point C.$E_{1}=\dfrac{k\timex 20\times 10^{-6}}{x^2}$

• The electric field from a point charge 80 micro coulomb at point C.$E_{2}=\dfrac{k\timex 80\times 10^{-6}}{(18-x)^2}$

The net electric field at point C is zero

$Thus, E_1=E_2\dfrac{k\timex 20\times 10^{-6}}{x^2}=\dfrac{k\timex 80\times 10^{-6}}{(18-x)^2}\dfrac{1}{x^2}=\dfrac{4}{(18-x)^2}18-x=2xx=6$