Assertion (A) : A step-up transformer cannot be used as a step-down transformer.

Reason (R) : A transformer works only in one direction.

Equipotentials at a large distance from a collection of charges whose total sum is not zero are -

Four charges $$-$$q, $$-$$q, +q and +q are placed at the corners of a square of side 2 L is shown in figure. The electric potential at point A midway between the two charges +q and +q is -

Case Study :

An experiment was set up with the circuit diagram shown in figure. Given that R₁ = 10 $$\Omega$$, R₂ = R₃ = 5 $$\Omega$$, r = 0 $$\Omega$$ and E = 5 V

The points with the same potential are -