Question

two equal and opposite chargers 4*10 power-8 columb. when placed 2*10 power-2 away from dipole.if this dipole is placed in external field 4*10 power 8 newton/columb.find value of maximum torque and work done rotating through 180 degree

Answer 1

Answer:

q=4×10 −8

l=2×10 −2cm

E=4×10 8

Dipole moment =ql=4×10 −8 ×2×10 −4

=8×10 −12

max toeque =PEsinθ=8×10 −12 ×4×10 8

=32×10 −4

work done =PE(cosθ 1−cosθ 2 )=32×10 −4 (1−(−1))=64×10 −4

Answer 2

SOLUTION -:

Toque acting on dipole

π = PE sin Ø or π = q x 2 l E sin Ø

Given -:

q = 4 x 10 -⁸ C , 2L = 2 x 10 -² × 10-² m

E = 4 × 10⁴ N/ C & for maximum torque ø = 90⁰

because,,

torque π = 4 x 10-⁸ x 2 x 10-⁴ x 4 x 10⁴

sin 90⁰

π = 32 x 10-⁴ N - m

work done rotating from Angle ∅

W = PE ( 1 - cos Ø ) or W = q x 2l E (1- cos Ø )

Work for 180° rotation

W = 4 x 10-⁸ x 2 x 10-⁴ x 4 x 10-⁴

( 1- cos 180° )

=> 64 x 10 -⁴ J