Impedance comprises of two things: reactance and resistance, making the resistance a subset of impedance. Impedance is a progressively broad term for resistance that additionally incorporates reactance. Impedance and reactance are both given in units of 'ohms' simply like resistance.

Resistance

Resistance is an idea utilized for DC (coordinate flows) while impedance is the AC (exchanging current) identical. Resistance is the restriction of an enduring electric flow. Unadulterated resistance does not change with recurrence, and normally the main time just resistance is considered is with DC (coordinate flow - not evolving) power.

Resistance Vs Impedance

Resistance is the restriction of the electrical flow stream.

Resistance happens in AC and DC circuits.

Notwithstanding Resistance, AC circuits additionally show Reactance.

Reactance is likewise the restriction to the electrical flow stream.

By its very nature, a DC circuit won't display any type of Reactance, along these lines restriction the o the current stream will dependably be estimated in Resistance.

Reactance exists in two structures, Capacitive and Inductive.

The blends of Reactance and Resistance is called Impedance

Impedance can hence be thought of as the resistance of the electrical flow stream in an AC circuit.

Because of the idea of AC circuits Reactance is constantly present

Any estimation of the restriction of the current stream in an AC circuit will dependably be estimated in Impedance.

Impedance and Resistance are both estimated in Ohms and are exchangeable in numerous electrical recipes by and by i.e, Ohms Law.

As an oversimplified general view, Impedance can be thought of as Resistance in an AC circuit.

Limitations of Terzaghi Theory The value of the coefficient of consolidation has been assumed to be constant. The distance d of the drainage path cannot be measured accurately in the field. The thickness of the deposit is generally variable, and an average value has to be estimated. There is sometimes difficulty 1n locating the drainage face, sometimes thin previous seams that can act as good drainage face are missed in the boring operations. The equation is based on the assumption that the consolidation is one-dimensional. In the field, the consolidation is generally 3-dimensional. The lateral drainage may have a significant effect on the time rate of consolidation. The initial consolidation and secondary consolidation have been neglected. Sometimes these form an important part of the total consolidation. In actual practice, the pressure distribution may be far from linear or uniform. Read More Muller-Breslau principle

Price Guard Wire Method Some form of Price Guard Wire Method is generally used to eliminate the errors caused by leakage currents over insulation. Fig. 3.14 illustrates the operation of This Method. In fig 3.14(a), a high resistance mounted on a piece of insulating material is measured by the ammeter voltmeter method. The micro-ammeter measures the sum of the current through the resistor (IR) and the current through the leakage path around the resistor. The measured value of resistance computed from the readings indicated on the voltmeter and the microammeter, will not be a true value but will be in error. Figure 3.14 Application of guard circuit for measurement of high resistance In fig, 3.14 (b), the guard terminal has been added to the resistance terminal block. The guard terminal surrounds the resistance terminal entirely and is connected to the battery side of the micro-ammeter. The leakage current IL now

Negative booster A negative booster is employed to conform to the regulation that the potential difference between any two points of the rail return shall not exceed 7 V. Two boosters, positive and negative, are used which are mechanically coupled together and driven by a DC motor. The positive booster is connected to the trolley wire (near the generating station) and the negative booster (separately excited) is connected to the track rail. The 'positive booster' adds voltage to the line while the 'negative booster lowers the potential of the point it is connected to. As we go along the trolley wire away from the generating station/sub-station, the potential drop increases, and the voltage of the trolley wire falls. Since the current returns via the track rail points away from the generating station acquire high potentials. This potential is brought down by the negative boost provided by the negative booster. When the load is sufficiently far aw