Question 648: Electrostats & Capacitance

Question

A capacitor of capacitance C = 900 pF is charged fully by 100 V battery B as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance C = 900 pF as shown in figure (b). The electrostatic energy stored by the system (b) is

Accepted Answer

q
1
= CV
= 900 $$	imes$$ 10
$$-$$12
$$	imes$$ 100
= 9 $$	imes$$ 10
$$-$$8
C
$$V = {{{C_1}{V_1} + {C_2}{V_2}} \over {{C_1} + {C_2}}}$$
$$ = {{9 	imes {{10}^{ - 8}} + 0} \over {1800 	imes {{10}^{ - 12}}}} = {{100} \over 2} = 50$$ V
$$U = {1 \over 2}({C_1} + {C_2}){V^2}$$
$$ = {1 \over 2} 	imes 1800 	imes {10^{ - 12}} 	imes 50 	imes 50$$
$$ = 225 	imes {10^{ - 8}}$$
$$U = 2.25 	imes {10^{ - 6}}$$ J

Answer

4.5 $$	imes$$ 10$$-$$6 J

Answer

3.25 $$	imes$$ 10$$-$$6 J

Answer

2.25 $$	imes$$ 10$$-$$6 J

Answer

1.5 $$	imes$$ 10$$-$$6 J

Electrostats & Capacitance

A capacitor of capacitance C = 900 pF is charged fully by 100 V battery B as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance C = 900 pF as shown in figure (b). The electrostatic energy stored by the system (b) is

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