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mT (4) 4.4 T than I flows but can be in any direction. (3) there is no current. 35 A horizontal force 10 Nis applied to a block A as (4) displacement current of magnitude equal to shown infigure.The mass ofblocks A and B are I flows in the same direction as I.
For bridge balance, current must flow normally through all arms -> Diode must be FORWARD BIASED in series -> Circuit (3) has diode anode pointing from bottom node to right node!
For a bridge to achieve balance, the potential difference across the galvanometer G must be zero (V_top = V_bottom), which requires continuous current flow through all four resistive branches establishing a stable potential divider.
The DC source E is connected with its positive terminal on the left and negative terminal on the right. Current enters at the left node, divides into the upper and lower arms, and exits at the right node. In the bottom-right arm, the conventional current MUST flow from the lower central junction towards the right-hand junction connected to the negative terminal of the battery.
A p-n junction diode conducts current only when it is forward biased (p-side/anode at higher potential than n-side/cathode). In Circuit (3), the anode is connected to the bottom junction and cathode to the right junction, so it is forward biased and conducts freely. In Circuit (4), the diode is reverse biased, presenting near-infinite resistance and preventing current flow.
Therefore, only Circuit (3) allows proper forward-biased conduction through the diode in series with the 5 Ω resistor, making it the only circuit that can establish the required currents and achieve bridge balance.
Diagnose every choice: Know exactly why the right option works and why distractors fail.
Parallel diode clamps voltage and prevents linear bridge balance.
Cannot achieve balance.
Diode is properly forward-biased in the direction of conventional current flow.
Diode is reverse biased and acts as an open circuit (I = 0).
Students look at the resistor values and treat the diode as a plain wire, failing to check whether the diode arrow points with or against the battery current.
"A p-n junction diode conducts when forward-biased and acts as an open circuit when reverse-biased; bridge balance requires all arms to conduct."
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