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CBSE Class 12 Physics 2023 Delhi Set 3 Paper

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Question : 12 of 14
Marks: +1, -0
Two conductors, made of the same material have equal lengths but different cross-sectional areas A1A_1 and A2(A1>A2)A_2 (A_1 > A_2). They are connected in parallel across a cell. Show that the drift velocities of electrons in two conductors are equal.
Solution:     👈: Video Solution
When two conductors are connected parallel to a cell, then the potential difference across the two conductors will be same.
 So, V1=V2\text{ So, } V_1 = V_2
 Or, I1R1=I2R2 (from Ohm’s law) \text{ Or, } I_1 R_1 = I_2 R_2 \text{ (from Ohm's law) }
 Or, neA1vd1R1=neA2vd2R2\text{ Or, } n e A_1 v_{d 1} R_1 = n e A_2 v_{d 2} R_2
 Or, A1vd1R1=A2vd2R2\text{ Or, } A_1 v_{d 1} R_1 = A_2 v_{d 2} R_2
 Or, A1vd1ρlA1=A2vd2ρlA2\text{ Or, } A_1 v_{d 1} \rho \frac{l}{A_1} = A_2 v d_2 \rho \frac{l}{A_2} ( since R=ρlA)\left(\text{ since } R = \rho \frac{l}{A}\right)
∴vd1=vd2\therefore v_{d 1} = v_{d 2}
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