### Physics - Capacitance

#### Question - 1

Three identical capacitors are connected together differently. For the same voltage to every combination, the one that stores maximum energy is

• A the three in series
• B the three in parallel
• C two in series with the third in parallel with it
• D two in parallel with the third in series with it

#### Question - 2

Two condensers of capacities 2C and C are joined in parallel and charged upto potential V. The battery is removed and the condenser of capacity C is filled completely with a medium of dielectric constant K. The potential difference across the capacitors will now be

• A $\frac { 3V }{ K+2 }$
• B $\frac { 3V }{ K}$
• C $\frac { V }{ K+2 }$
• D $\frac { V }{ K }$

#### Question - 3

A capacitor with capacity 100 $\mu F$ is charged with a battery of 24 V. It is then connected to a battery of 12 V with positive plate is joined to positive terminal of battery. Heat developed in the process of flow of charge after connection is

• A greater than 7.2 mJ
• B less than 7.2 mJ
• C equal to 7.2 mJ
• D No heat is produced

#### Question - 4

A capacitor is made of two circular plates of radius R each, separated by a distance d << R. The capacitors is connected to a constant voltage. A thin conducting disc of radius r << R and thickness t << r is placed at a centre of the bottom plate. Then, the minimum voltage required to lift the disc, if the mass of the disc is m, is

• A $\sqrt { \frac { mg{ d }^{ 2 } }{ \pi { \varepsilon }_{ 0 }{ r }^{ 2 } } }$
• B $\frac { { \varepsilon }_{ 0 }\sigma }{ d }$
• C $\frac { \sigma }{ { \varepsilon }_{ 0 } } d$
• D None of these

#### Question - 5

Match the value of capacitance given in Column I with their values given in Column II and select the correct option from the choices given below

 Column I Column II A. Capacitance of parallel plate capacitor in air 1. $\frac { K{ \varepsilon }_{ 0 }A }{ d }$ B. Capacitance of parallel plate capacitor when a dielectric slab is inserted partially between the plates 2. $\frac { { \varepsilon }_{ 0 }A }{ \left( d-t \right) +\frac { t }{ K } }$ C. Capacitance of parallel plate capacitor when a dielectric slab is inserted fully between the plates. 3. $\frac { { \varepsilon }_{ 0 }A }{ d }$
• A A B C 1 2 3
• B A B C 3 2 1
• C A B C 3 2 1
• D A B C 2 3 1

#### Question - 6

A parallel plate condenser with a dielectric of dielectric constant K between the plates has a capacity and is charged to a potential V volt. The dielectric slab is slowly removed from between the plates and then reinserted. The net work done by the system in this process is

• A $\frac { 1 }{ 2 } \left( K-1 \right) { CV }^{ 2 }$
• B ${ CV }^{ 2 }\left( K-1 \right) K$
• C $\left( K-1 \right) { CV }^{ 2 }$
• D zero

#### Question - 7

A fully charged capacitor has a capacitance C. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity s and mass m. If the temperature of the block is raised by $\triangle T$, the potential difference V across capacitance is

• A $\sqrt { \frac { 2mC\triangle T }{ s } }$
• B $\frac { mC\triangle T }{ s }$
• C $\frac { ms\triangle T }{ C }$
• D $\sqrt { \frac { 2ms\triangle T }{ C } }$