JEE Advanced · Physics · 21. EMI
A conducting wire of parabolic shape, initially is moving with velocity in a non-uniform magnetic field as shown in figure. If and are positive constants and is the potential difference developed between the ends of the wire, then the correct statement(s) is/are:

- A is proportional to the length of the wire projected on the y-axis.
- B for
- C remains the same if the parabolic wire is replaced by a straight wire, initially, of length
- D for
Answer & Solution
Correct Answer
(A) is proportional to the length of the wire projected on the y-axis.
Step-by-step Solution
Detailed explanation
For calculating the motional emf across the length of the wire, let us project wire such that becomes mutually orthogonal. Thus, small emf 'dc' induced in elemental length of projected wire, will be -
\(\Rightarrow d \varepsilon=B v_0 d y=B_0\left[1+\left(\frac{y}{L}\right)^\beta\right] V_0 d y \)
\( \varepsilon=\int_0^L B_0\left(1+\left(\frac{y}{L}\right)^\beta\right) V_0 d y=\int_0^L B_0 \cdot\)\( V_0 \cdot d y+\int_0^L \frac{B_0 \cdot V_0}{L^\beta} y^\beta \cdot d y \)
\( =B_0 V_0 L\left[1+\frac{1}{\beta+1}\right]\)
emf in loop is proportional to for given value of .
Option is correct.
for
Option is correct.
Now, the length of the projection of the wire and length on the y-axis is thus the answer remain unchanged Option is correct.
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