If two bulbs are connected in parallel and one bulb blows out, what happens to the other bulb?

Question

Examoogle · Accepted Answer

The other bulb continues to glow with the same brightness

Explanation: In a parallel circuit, every component is connected directly across the supply voltage terminals, meaning each branch operates independently. When one bulb blows out (becomes an open circuit), the potential difference across the other bulb remains unchanged, allowing it to continue operating normally.

Working Principle: In a parallel arrangement, the voltage ($V$) across each load is equal to the source voltage, i.e., $V_{total} = V_1 = V_2$. Since the current through the healthy bulb is determined by Ohm's Law $I = \frac{V}{R}$, and neither the supply voltage ($V$) nor the resistance of the healthy bulb ($R$) changes, the current and power dissipation remain constant.

Key Formulas: $V = V_1 = V_2$ — Voltage distribution in parallel; $I_{total} = I_1 + I_2$ — Current distribution in parallel; $P = \frac{V^2}{R}$ — Power consumption of each bulb

Key Points: Parallel circuits ensure independent operation of loads.; The failure of one branch does not affect the voltage potential across other branches.; House wiring is primarily based on parallel connections to maintain constant voltage for all appliances.

Advantages: Independent operation of electrical devices.; Constant voltage supply across all parallel loads.; Easy addition or removal of circuits without affecting others.

Disadvantages: Higher complexity in wiring compared to series circuits.; Requires more conductor material for multiple parallel paths.

Applications: Domestic wiring systems.; Industrial power distribution.; Multimeter voltage measurements.

Additional Info: In a series circuit, blowing out one bulb acts as an open switch, breaking the entire path and turning off all other bulbs.. Parallel connections are the standard for 230V AC residential supply in India.

Answer: B is correct — In parallel circuits, the voltage across each load is constant, so one bulb failing does not change the operation of the others.

Exam Tip: Always remember: Series circuits share voltage, while parallel circuits share current but maintain identical voltage across branches.

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