Question

An electric dipole consists of two opposite charges each of magnitude 1uc separated by 2 cm. The dipole is placed in an external electric field of 105 N/C. Find: (i) The maximum torque exerted by the field on the dipole (ii) The work the external agent will have to do in turning the dipole through 180° starting from the position 0= 0° 2M​

Answer 1

Answer:

An electric dipole consist at two opposite charge each of magnitude =1μC=1×10

−6

C

distance =2cm

Exter field =10

5

N/C

maximum torque on the dipole =?

q=1×10

−6

C,2a=2cm

or, =0.02cm

∴ P=q×2a

=(1×10

−6

)×0.02

=2×10

−8

cm

Intensity of the external electric field, E=1.0×10

5

N/C

(i) Z

max

=pE=(2×10

−8

)(10×10

5

)=2×10

−3

N−m

(ii) Net work done in turning the dipole from 0

0

to 180

0

i.e W=∫

0

0

180

0

r

dθ=∫

0

0

180

0

pEsinθdθ

=pE[−cosθ]

0

0

180

0

=−pE(cos180

0

−cos0

0

)

=2pE

=2×(2×10

−8

)(1×10

5

)J

=4×10

−3

J