Single Choice

Calculate I for the given circuit diagram.

A10:00 AM
Correct Answer
B5:00 AM
C2.5 A
D20 A

Solution

For the wheatstone bridge part, the bridge resistance can be ignored. For this part, we have two branches each having two 5 ohm resistors.
$$\cfrac{1}{R_W}=\cfrac{1}{R_1}+\cfrac{1}{R_2}$$

where, $$R_1=R_2=5+5=10\ \Omega$$ because they are in series.

Hence, $$R_W=5\ \Omega$$

The wheatstone bridge is parallel to a 5 ohm resistor. Hence total equivalent resistance,
$$\cfrac{1}{R_{eq}}=\cfrac{1}{R_W}+\cfrac{1}{5}$$

$$\Rightarrow R_{eq}=2.5\ \Omega$$

$$I=\dfrac{V}{R}=\dfrac{25}{2.5}=10\ A$$


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