- Introduction
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- Alternating current and Alternating EMF
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- Average or mean current
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- Root Mean square value of AC
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- Phasor diagram
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- A.C through pure resistor
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- A.C through pure inductor
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- AC through pure capacitor
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- Circuit containing inductance and resistance in series
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- Circuit containing capacitance and resistance in series
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- LCR series circuit

The circuit is shown below.

Currently the switch is in position A and steady current is flowing to the circuit. Capacitor is uncharged. At t=0, switch is instanously moved to position B.

Here $\omega = \frac {1} {\sqrt LC}$

Solution

Solution

a) The electric oscillations of time period $2\pi \sqrt{LC}$ are produced in the LC circuit

b) The total energy remains conserved and is equal to $\frac {1}{2}L \frac {V_0^2}{R}$

c) The maximum current in the circuit is V

d) None of these

Solution

An LR circuit is connect to Voltage source V

a) The rate at which energy is being stored in Inductor is given by $\frac {.63 V_0^2}{R}$

b) Power loss in the resistor is given by $\frac {.40 V_0^2}{R}$

c) The rate of change of current is $\frac {.37 V_0^2}{R}$

d) Current is 63% of the maximum value

Solution

A circuit is shown below in Figure

It is given

L=R

Which of the following is true

a) The total current will instantly rise to its final value V

b) The current will zero in LR branch and have value V

c) The current will rise with time in the LR circuit and decrease with time in LC circuit

d) Total current in the circuit will always be V

Solution

A sinusoidal voltage of frequency f=60Hz and peak value 150V is applied to a series LR circuit

Where L=40mH and R=20ohm

a) The instantaneous current is 2.344 A

b) The instantaneous voltage across inductor is 83.29 V

c) The instantaneous voltage across resistor is 46.88 V

d) The total voltage applied is 130 V

a) Average power into the circuit is 360 W

b) I

c) V

d) None of these

Solutions for Questions 6-8

A coil of inductance .50H and resistance 100 ohm is connected to 240 V,50Hz AC supply

Which of the following is true

a) I

b) The time lag between voltage maximum and current maximum is 3.2X10

c) Maximum Voltage is 339.36 V

d) None of these

Solution

(i) The time constant of the circuit,

(ii) The maximum charge on the capacitor after a switch in the circuit is closed, and

(iii) The current in the circuit at the instant just after the switch in the circuit is closed

Class 12 Maths Home page Class 12 Physics Home page

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- university physics with modern physics by Hugh D. Young 13th edition
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