Question

Two charges of 5 pc & 20 uc are placed 20 cm apart. Calculate the
work done in bringing the charges closer to 15 cm apart.​

Answer 1

Answer:

Let the two charges placed at two points of line AB as A and B whose  distance is 20 cm and O is the midpoint of the line AB

Distance between the two charges, AB=20 cm

∴AO=OB

Net elctric at O=E

The Electric field at point O caused by +5\mu C charge,

E  

1

​  

=  

4πε  

0

​  

(AO)  

2

 

5×10  

−6

 

​  

 

     =  

4πε  

0

​  

(10×10  

−2

)  

2

 

5×10  

−6

 

​  

 N/C toward +5μC

where,

ε  

0

​  

=Permittivity of free space

4πε

1

​  

=9×10  

9

Nm  

2

C  

−2

 

Magnitude of electric field at point O cause by +10\mu C charge,

E  

1

​  

=  

4πε  

0

​  

(AO)  

2

 

10×10  

−6

 

​  

 

     =  

4πε  

0

​  

(10×10  

−2

)  

2

 

10×10  

−6

 

​  

 N/C towards +10μC

∴E=E  

1

​  

+E  

2

​  

 

=  

(10×10  

−2

)  

2

 

9×10  

9

×15×10  

−6

 

​  

 

=13.5×10  

6

 N/C towards +5μC