From the figure it can be concluded that the voltmeter reads 5 volts as shown in the figure below. Based on the voltmeter and ammeter readings in the measuring network, determine the value of the resistor R Here Current I = 1/2 A = 0.5 A Voltage V = 5 V R = V/I = 0.5/5 R = 10Ω
Voltage regulation:- When a transmission line is carrying current, there is a voltage drop in the line due to resistance and inductance of the line. The result is that the receiving end voltage (VR) of the line is generally less than the sending end voltage (Vs). This voltage drop (Vs − VR) in the line is expressed as a percentage of receiving end voltage VR and is called voltage regulation.
The difference in voltage at the receiving end of a transmission line between conditions of no-load and full-load is called voltage regulation and is expressed as a percentage of the receiving end voltage. Mathematically,
% Voltage regulation = (Vs − VR) ⁄ VR × 100
Obviously, it is desirable that the voltage regulation of a transmission line should be low i.e., the increase in load current should make very little difference in the receiving end voltage. In the transmission line, the voltage regulation is negative whenever the receiving end voltage VR is Greater than the sending end voltage.
The regulation will depend upon the power factor of the load. If the power factor is lagging, the voltage at the sending end is more than that at the receiving end. Hence, voltage regulation is positive. On the other hand, if the power factor is leading, the voltage at the sending end will be somewhat less than that at the receiving end. In that case, the regulation is negative.
Torque speed characteristic of induction motor
Motoring mode: 0 ≤ s ≤ 1
For this range of slip, the load resistance in the circuit is positive, i.e. torque developed is in the direction in which the rotor rotates.
In this region the value of slip lies between 0 to 11 i.e., slip is positive.
The motor rotates in the same direction as that of a rotating magnetic field.
At s = 0 (synchronous speed), the torque produced by the motor is zero because the induced voltage in the rotor is zero when N= Ns.
The torque increases as the slip increases while the air gap flux remains constant.
The torque-slip characteristic from no-load to somewhat beyond full-load is almost linear.
Generating mode: s <0
In this operating mode, the slip s is negative i.e., s < 0. The slip will be negative if and only if the rotor speed N is greater than the synchronous speed Ns (N> Ns). However, the rotor and R.M.F both rotate in the same direction.
In this region, the motor acts as a generator and return the power back to a.c. source.
Braking or plugging Mode: s > 1
In this region, the value of slip is greater than 1 and the rotor rotates in the opposite direction of the rotating magnetic field.
This is achieved by interchanging any two phases of the stator supply.
Galvanized steel conductors do not corrode, and possess high resistance. Hence such Wires are used in telecommunications circuits, earth wires, guard wire, stray wire, etc.
Mutual inductance between two coupled coils is given by the relation
M = K√L1L2
L1L2 = Inductance of the coil
K = Coefficient of coupling
When K = 1 coils are said to be tightly coupled and if K is a fraction the coils are said to be loosely coupled.
∴ m ≤ (L1 L2 )0.5