Question

Two identical air filled parallel plate capacitors are charged to the same potential in the manner shown by closing the switch $ S $ . If now the switch $ S $ is opened and the space between the plates is filled with a dielectric of relative permittivity $ \varepsilon_{r} $ , then

• A. the potential difference as well as charge on each capacitor goes up by a factor $ ε_r $
• B. the potential difference as well as charge on each capacitor goes down by a factor $ ε_r $
• C. the potential difference across $ A $ remains constant and the charge on $ B $ remains unchanged
• D. the potential difference across $ B $ remains constant while the charge on $ A $ remains unchanged

Answer 1

Answer: (C)

When switch $S$ is opened, capacitor $A$ is still connected with battery. Therefore, potential difference across $A$ remains constant. As $B$ is disconnected from battery, charge on $B$ remain fixed.