a) What do you expect to be the waveform of the induced emf as a permanent bar m

Question

a) What do you expect to be the waveform of the induced emf as a permanent bar magnet is introduced into the coil? As it is withdrawn from the same end that it came in? As it is withdrawn from the opposite end? As it is introduced at twice the speed?

b) A triangle current waveform is applied to the source coil. This is a current that alternately increases with time at a certain rate, and then decreases with time at the same constant (negative) rate, repeating the cycle at some frequency f.
          i. Draw (qualitatively) the triangle current waveform versus time
         ii. Draw (qualitatively) the expected magnetic field versus time
         iii. Draw (qualitatively) the magnetic flux %u03C6m intercepting the detector coil versus time

          iv. Draw (qualitatively) d%u03C6m/dt.

Explanation / Answer

The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load, to the apparent power in the circuit,[1][2] and is adimensionless number between -1 and 1. Real power is the capacity of the circuit for performing work in a particular time. Apparent power is the product of the current and voltage of the circuit. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power will be greater than the real power. A negative power factor occurs when the device which is normally the load generates power which then flows back towards the device which is normally considered the generator.[3][4][5]

In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred. The higher currents increase the energy lost in the distribution system, and require larger wires and other equipment. Because of the costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers where there is a low power factor.

Linear loads with low power factor (such as induction motors) can be corrected with a passive network of capacitors or inductors. Non-linear loads, such as rectifiers, distort the current drawn from the system. In such cases, active or passive power factor correction may be used to counteract the distortion and raise the power factor. The devices for correction of the power factor may be at a central substation, spread out over a distribution system, or built into power-consuming equipment.

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