9. two unequal charges repel each other with a force of magnitude f. after both charges are tripled in magnitude, the new repelling force between them has magnitude
3 f
6 f
9 f
27 f

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9. 9 times force

8. 7000 N/C directed towards q₂

Explanation:

9.

Let the two charges be and separated by distance r. Then the force of repulsion is given as :

where, k is the Coulomb's constant.

When the magnitude of the charges is tripled: and , the new force of repulsion, force' is:

8.

The electric field is given by:

where q is the charge and r is the distance of the point from the charge where electric field is required to be found.

It is given that,

Electric field due to charge at point a is:

Electric field due to charge at point a is:

Thus, net electric field due to both charges at a is

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6

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