Multiple choice (show your work if any): 

1) Two point charges q1=-10^-5 C and q2=-9×10^-5 C are placed respectively at two points A and B 40 cm apart. The electric field is null at a point C of [AB] such that : 

a) AC=50cm b) AC=10cm c) AC=20cm d) point C doesn't exist 

2) Same given. The electric field is null at a point C outside [AB] such that :

 a) AC=50cm b) AC=30cm c) AC=20cm d) point C does not exist

do your own work

answer:C does not exist

hey vicky solve it like this:
since electric field at C is equal to 0.therefore,
Eac=Ebc
since we know that electric field ,E=kq/r^2
let r be represented by x
where k=propotionality constant
#k*10^-5/x^2=k*9*10^-5/(40-x)^2
on solving u get a quadratic equation as
8x^2+80x-1600=0
this equation has no solution
hence C at distance x does not exist

To find the correct answer to these multiple-choice questions, we need to use the concept of electric field intensity, which is given by the equation:

E = k * (q1 / r1^2) + k * (q2 / r2^2)

Where:
- E is the electric field intensity
- k is the electrostatic constant (k = 9 * 10^9 Nm^2/C^2)
- q1 and q2 are the magnitudes of the point charges
- r1 and r2 are the distances between the charges and the point C

Let's solve each question step by step:

1) Electric field is null at point C on AB.

This means that the net electric field intensity at point C is zero. The equation becomes:

0 = k * (q1 / r1^2) + k * (q2 / r2^2)

Plugging in the values given:
0 = k * (-10^-5 / r1^2) + k * (-9×10^-5 / r2^2)

To cancel out the common factor of k, we can divide both sides of the equation by k:

0 = (-10^-5 / r1^2) + (-9×10^-5 / r2^2)

Now we have a single equation with two unknowns. Since we know the distances on AB (40 cm), we can use the relationship r1 + r2 = 40 cm.

We can substitute r1 = 40 cm - r2 into the equation:

0 = (-10^-5 / (40 - r2)^2) + (-9×10^-5 / r2^2)

Now we can solve this equation to find the value of r2 and then calculate r1 = 40 cm - r2.

2) Electric field is null at point C outside AB.

Using the same steps as in question 1, we have the equation:

0 = k * (q1 / r1^2) + k * (q2 / r2^2)

Plugging in the values given:

0 = k * (-10^-5 / r1^2) + k * (-9×10^-5 / r2^2)

Dividing by k:

0 = (-10^-5 / r1^2) + (-9×10^-5 / r2^2)

Since point C is outside AB, r1 and r2 are both positive. Hence, there won't be a cancellation of terms like in question 1.

Now you can solve these equations to find the values of r1 and r2 and select the correct answer choice from the given multiple-choice options.