Question
The power factor of a good choke coil is
✓
Answer
(a)$\cos \phi = \frac{R}{Z}$. In choke coil $\phi \approx 90^\circ $so $\cos \phi \approx 0$
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
If the resistivity of a potentiometer wire be $\rho $ and area of cross-section be $A$, then what will be potential gradient along the wire
→A horizontal plane supports a stationary vertical cylinder of radius $R = 1\ m$ and a disc $A$ attached to the cylinder by a horizontal thread $AB$ of length $l_0 = 2\ m$ (seen in figure, top view). An intial velocity ($v_0 = 1\ m/s$) is imparted $AB$ to the disc as shown in figure. .......... $\sec$ long will it move along the plane until it strikes against the cylinder ? (All surface are assumed to be smooth)
→The output voltage (taken across the resistance) of a $L-C-R$ series resonant circuit falls to half its peak value at a frequency of $200 \,Hz$ and again reaches the same value at $800 \,Hz$. The bandwidth of this circuit is ............. $\,Hz$
→A long wire carries a steady current. It is bent into a circle of one turn and the magnetic field at the centre of the coil is $B$. It is then bent into a circular loop of $n$ $turns$. The magnetic field at the centre of the coil will be
→A tiny spherical oil drop carrying a net charge $q$ is balanced in still air with a vertical uniform electric field of strength $\frac{81 \pi}{7} \times 10^5 \mathrm{Vm}^{-1}$. When the field is switched off, the drop is observed to fall with terminal velocity $2 \times 10^{-3} \mathrm{~ms}^{-1}$. Given $\mathrm{g}=9.8 \mathrm{~ms}^{-2}$, viscosity of the air $=1.8 \times 10^{-5} \mathrm{Ns} \mathrm{m}^{-2}$ and the density of oil $=$ $900 \mathrm{~kg} \mathrm{~m}^{-3}$, the magnitude of $\mathrm{q}$ is
→A uniform rope having some mass hanges vertically from a rigid support. A transverse wave pulse is produced at the lower end. The speed $(v)$ of the wave pulse varies with height $(h)$ from the lower end as:
→The magnifying power of a telescope is $9.$ When it is adjusted for parallel rays the distance between the objective and eyepiece is $20\; cm.$ The focal length of lenses are
→A prism $(\mu = 1.5)$ has the refracting angle of $30^o $. The deviation of a monochromatic ray incident normally on its one surface will be ($sin 48^o 36’ = 0.75$)
→Let ${\lambda _\alpha }$, ${\lambda _\beta }$ and ${\lambda '_\alpha }$ denote the wavelengths of the $X-$ rays of the ${K_\alpha },\,{K_\beta }$ and ${L_\alpha }$ lines in the characteristic $X-$ rays for a metal
→ A nucleus $_n{X^m}$ emits one $\alpha$ particle and two $\beta$ particles. The resulting nucleus is
→