A parellel plate capacitor with plate speration d is charged with a battery so that energy stored is #"U"#. If a plate of dielectric #"K"# and thickness d is placed betweeen the plates of capacitor and battery remains connected. The work by battery is?
Options:

#"KU"#

#"2U(K  1)"#

#"U(K  1)"#

#"2KU"#
Options:

#"KU"# 
#"2U(K  1)"# 
#"U(K  1)"# 
#"2KU"#
1 Answer
Mar 14, 2018
Explanation:
The energy stored in a capacitor is given by
When the dielectric is introduced, the capacitance increases by a factor of
So, the charge stored in the capacitor grows from
Note that this is twice the energy gained by the capacitor.