Competitive Thinking

A coil of self-inductance $L$ is connected in series' with a bulb $B$ and an A C source. Brightness of the bulb decreases when

A current of $25/\pi \mathrm{Hz}$ frequency is passing through an A.C. circuit having series combination of $R=100 \mathrm{\Omega }$, $L=2 \mathrm{H}$ and the phase difference between voltage and current is,

A coil of inductive reactance $1/\sqrt{3} \mathrm{\Omega }$ and resistance $1 \mathrm{\Omega }$ is connected to a $200 \mathrm{V}, 50 \mathrm{Hz}$ A.C. supply. The time lag between maximum voltage and current is
 

A series $R-C$ circuit is connected to an alternating voltage source. Consider two situations:
(i) When capacitor is air filled.
(ii) When capacitor is mica filled.
Current through resistor is $i$ and voltage across capacitor is $V$, then:
 

The frequency of the output signal becomes times by doubling the value of the capacitance in the LC oscillator circuit,
 

A $16 \mathrm{\mu }\text{F}$ capacitor is charged to $20 \mathrm{V}$. The battery is then disconnected and a pure $40 \mathrm{mH}$ coil is connected across the capacitor, so that LC oscillations are set up. The maximum current in the coil is
 

The natural frequency of an LC circuit is $125 \mathrm{kHz}.$ When the capacitor is totally filled with a dielectric material, the natural frequency decreases by $25 \mathrm{kHz}$. Dielectric constant of the material is nearly

An alternating e.m.f. of frequency, $f=\frac{1}{2\pi \sqrt{LC}}$ is applied to a series LCR circuit. For this frequency of the applied e.m.f.,