wiz-icon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

A unit positive charge has to be brought from infinity to a mid-point between two charges, 20 μC and 10 μC separated by a distance of 50 m. How much work will be required by an external force?

A
0.1×104 J
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
1.1×104 J
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
C
2.1×104 J
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
3.1×104 J
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

The correct option is B 1.1×104 J
Given:
Point charge, qo=1 C

Let point M be the mid-point between the two charges.


At point M, total potential, VM=Vq1+Vq2
VM=kq1r1+kq2r2
VM=9×109×20×10625+9×109×10×10625
VM=1.1×104 V

We know, VM=Wext(M)qo
So, 1.1×104=Wext(M)1
Wext(M)=1.1×104 J

External force will have to do 1.1×104 J of work.

Why this question?Since potential at mid-point is greater than potential at infinity (v=0),the movementof charge is against its natural tendency.This gives hint that work has to be done by external force.

flag
Suggest Corrections
thumbs-up
8
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Potential Difference
PHYSICS
Watch in App
Join BYJU'S Learning Program
CrossIcon