An empty capacitor is connected to a 24.0 V battery andcharged up. The capacitor

Question

An empty capacitor is connected to a 24.0 V battery andcharged up. The capacitor is then disconnected from the battery,and a slab of dielectric material ( = 3.5) isinserted between the plates. Find the amount by which the potentialdifference across the plates changes. Specify whether the change isan increase or a decrease.
The voltage will decrease by ?? V An empty capacitor is connected to a 24.0 V battery andcharged up. The capacitor is then disconnected from the battery,and a slab of dielectric material ( = 3.5) isinserted between the plates. Find the amount by which the potentialdifference across the plates changes. Specify whether the change isan increase or a decrease.
The voltage will decrease by ?? V

Explanation / Answer

   Let the capacitance of the capacitor be'C0'.    Initial charge oncapacitor   Q   =   C0* V0                                              =   24.0*C0             When the capacitor is disconnected from thebattery and dielectric is inserted, charge still remains the same.Hence    Q   =   C *V    Where   C   =   k* C0 is new capacitance with dielectric of dielectricconstant 'k'             V   =   newvoltage between plates of capacitor    clearly      C* V   =   24.0 * C0             k* C0 * V   =   24.0 *C0          =>   V   =   24.0/ k                           =   24.0/ 3.5                      =   6.857   V    i.e. the voltage across capacitor willdecrease by   V0   -   V   =   24.0-6.857   =   17.143   V.             k* C0 * V   =   24.0 *C0          =>   V   =   24.0/ k                           =   24.0/ 3.5                      =   6.857   V    i.e. the voltage across capacitor willdecrease by   V0   -   V   =   24.0-6.857   =   17.143   V.

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