Question

Eels are able to generate current with biological cells called electroplaques. The electroplaques in an eel are arranged in 100 rows, each row stretching horizontally along the body of fish containing 5000 electroplaques. The arrangement is suggestively shown in the figure. Each electroplaque has an emf of $0.15\, V$ and internal resistance of $0.25\, \Omega$. The water surrounding the eel completes a circuit between the head and its tail. If the water surrounding it has a resistance of $500\, \Omega$, the current, an eel can produce in water is about

• A. 1.5 A
• B. 3.0 A
• C. 15 A
• D. 30 A

Answer 1

Answer: (A)

In each row all the 5000 electroplaques are connected in series.
Therefore, equivalent $emf =0.15 \times 5000=750\, V$
Equivalent resistance $=0.25 \times 5000=1250\, \Omega$
All 100 rows are connected in parallel.
Therefore, voltage $=750\, V$
Equivalent resistance $=\frac{1250}{100}=12.5\, \Omega$
Thus, resultant circuit of eel becomes
Current across $500\, \Omega=\frac{750\, V }{(12.5+500)\, \Omega}=1.5\,A$