Electric Charges and Fields

JEE Main 2024 (Online) 27th January Morning ShiftNumericalHard📈 Topic in 2% papers+4

Ques. 1JEE Main 2024, 27 January (Morning Shift)

A thin metallic wire having cross sectional area of 10-4 m2 is used to make a ring of radius 30 cm. A positive charge of 2 C is uniformly distributed over the ring, while another positive charge of 30 pC is kept at the centre of the ring. The tension in the ring is N; provided that the ring does not get deformed (neglect the influence of gravity). (given, 14 0 = 9 109 SI units)

Answer

Solution

[figure]

Element d : dQ = Q2 d , pushed out by q0

Equilibrium: 2T d 2 = kq0 dQR2 T d = kq0Q2 R2d

T = kq0Q2 R2 = 9 109 30 10-12 2 2 (0.3)2

= 0.270.09 = 3 N

Answer: 3

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Ques. 2JEE Main 2024, 27 January (Evening Shift)

Two charges of -4 and +4 are placed at the points A(1, 0, 4) m and B(2, -1, 5) m located in an electric field E=0.20 i V/cm. The magnitude of the torque acting on the dipole is 8 10-5 Nm, where = .

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