A railway track running north-south has two parallel rails 1 m apart. Calculate the value of induced emf between the rails, when a train passes at a speed of 25 m/s. The vertical component of earth's magnetic field at that place is $0.3 × 10^{-4} Wbm^{-2}$.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → $7.5 × 10^{-4} V$
$\text{Given: Distance between rails } l = 1~\text{m}$
$\text{Speed of train } v = 25~\text{m/s}$
$\text{Vertical component of Earth's magnetic field } B = 0.3 \times 10^{-4}~\text{Wb/m}^2$
$\text{Induced emf between rails is given by:}$
$\mathcal{E} = B \cdot l \cdot v$
$\mathcal{E} = (0.3 \times 10^{-4}) \cdot 1 \cdot 25$
$\mathcal{E} = 7.5 \times 10^{-4}~\text{V}$
$\text{Answer: } \mathcal{E} = 7.5 \times 10^{-4}~\text{V}$