NEETPhysicsAlternating CurrentMCQ+4 / −1
A series R-C circuit is connected to an alternating voltage source. Consider two situations :
(a) When capacitor is air filled.
(b) When capacitor is mica filled.
Current through resistor is and voltage across capacitor is then
(a) When capacitor is air filled.
(b) When capacitor is mica filled.
Current through resistor is and voltage across capacitor is then
- A
- B
- C
- D
View written solutionFree
Correct answer: D
For series R – C circuit, capacitive reactance,
Z= $$\sqrt {{R^2} + {{\left( {{1 \over {C\omega }}} \right)}^2}} $$
Current through resistor, i = Current in the circuit
= $${V \over {{Z_c}}} = {V \over {\sqrt {{R^2} + {{\left( {{1 \over {C\omega }}} \right)}^2}} }}$$
Voltage across capacitor, V = iXC
= $$ {V \over {\sqrt {{R^2} + {{\left( {{1 \over {C\omega }}} \right)}^2}} }} \times {1 \over {C\omega }}$$
= $${V \over {\sqrt {{R^2}{\omega ^2}{C^2} + 1} }}$$
When mica is introduced capacitance will increase, hence voltage across capacitor gets decrease.
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