In the circuit shown the variable resistance X is to be adjusted such that the ideal ammeter reads the same in both the positions of the key, when connected independently to 1 and then to 2. The reading of the ammeter is 2A. If E = 10 V, then x is:

Explanation

To solve this problem, we use Ohm's Law and the concept of equivalent resistance. We need the same current of 2A through the ammeter in both scenarios, which implies that the total resistance in the circuit must remain the same. Given that E = 10V and I = 2A, we apply the formula E = IR, which gives us R = E/I = 10V/2A = 5 Ω. This is the required resistance that allows the current to remain constant at 2A.Option A is correct because 5 Ω is the resistance needed. Options B and C are incorrect because they suggest resistance values that would change the current in the circuit. Option D is incorrect because the correct resistance can indeed be determined with the given information.