What is the effective resistance between the points a and d? a) 1.3 ω b) 2.2 ω c) 10 ω d) 12 ω

B) 2.2 Ω

Explanation:

The resistor between B and C is connected in parallel to the resistor between C and D (because their ends are connected to the same points: C on one side and B (which has same voltage as D) on the other side, so they have same potential difference across them.

So their equivalent resistance is

The resistor between A and B, instead, is short-circuited, because the current flows through the upper branch of the circuit (connecting A with C), which has zero resistance (it is a wire without any resistor). This means that the resistor between A and B should not be considered: so, the total resistance of the circuit is

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