⇒ The electric potential at a point is defined as the work done in bringing the unit positive charge ( +1C) from infinity to that point. The work done is independent of the path taken. Its unit is Volt (V).
⇒ Potential Difference (pd or V) is a measure of the difference in charge between two points in a conductor. Its unit is Volt (V).
⇒ The difference in charge produced by the battery is stored in the battery as electrical potential energy and is called electromotive force (shortened to emf). Electromotive force is also measured in volts. Its unit is Volt (V).
⇒ Electric flux is a measure of how much the electric field vectors penetrate through a given surface. The SI unit of electric flux is N.m2/C.
Electrical potential, Potential difference, Electromotive force has the same SI unit i.e Volt (V). Hence Electric flux is alike from others.
The steady direct current distributes itself uniformly over the whole section of a conductor but the alternating current does not distribute uniformly rather than it tends to concentrate near the surface of a conductor. In fact in the AC system, no current flows through the core and the entire current is concentric at the surface regions. This phenomenon is called skin effect.
The skin effect causes the effective resistance of the conductor to increase with the frequency of the current. The skin effect is due to eddy currents set up by the AC current. The skin effect has practical consequences in the design of radiofrequency and microwave circuits and to some extent in AC electrical power transmission and distribution systems.
The resistivity of iron at 20°C is 9.71 × 108
The resistivity of silver at 20°C is 1.59 × 108
The resistivity of Glass at 20°C is 1.10 × 109
The resistivity of nichrome at 20°C is 100 × 108
Hence silver is the least resistive material in the given option.
A practical parallel resonance circuit is represented by an inductance and a resistance id one branch and a capacitance in other branches.
At resonance in a practical parallel resonance circuit, the impedance is maximum. Hence, it is called a rejector circuit, and it exhibits the property of voltage magnification.
Z = L/CR
The strength of a magnetic field is specified by the magnetic induction B or by the magnetic field strength H. A current I through a long, straight wire produces a magnetic field with strength H = I/2πr at a distance r from the wire.
H = 1 A/m
I = 10 A
H = I/2πr
1 = 10/2πr
r = 10/2π
In order to achieve uniform illumination over a surface, the number of luminaries must be placed suitably. The space-height ratio plays a vital role in deciding the height of lamps from floor level and their spacing.
Space to height ratio
It is defined as the ratio of horizontal distance between adjacent lamps to the height of their mountings.
In order to obtain almost uniform illumination over the working plane, the distance between the lamps should not be too much. An ideal scheme could be developed, when there is a large number of small size lamps. But this would increase the installation cost. To have uniform illumination, the ratio of the spacing between the lamps and their height above the working plane (i.e., space-height ratio) should normally lie between 1 and 2.