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प्रश्न
Answer the following question.
Draw the diagram of a device that is used to decrease high ac voltage into a low ac voltage and state its working principle. Write four sources of energy loss in this device.
उत्तर
A transformer is a device that is used to either increase or decrease the ac voltage level. In order to decrease the high ac voltage level into a low ac voltage level we need a step-down transformer, whose diagram is as follows:
Working Principle:
A transformer works on the principle of electromagnetic induction. Alternating current in the primary coil produces a changing magnetic flux due to this an induced current is set up in the secondary coil. Losses in a transformer: Copper loss - The windings of the transformer have finite resistance due to which some energy is lost in the form of heat. It can be diminished using thick copper wires.
Iron loss - Loss is in the bulk of iron core due to the induced eddy currents in the iron core. It is minimized by using a thin laminated core.
Hysteresis loss - Alternating magnetizing and demagnetizing of the iron core causes the loss of energy in the form of heat. It is minimized using a special alloy of the iron core with silicon that has low hysteresis loss.
Magnetic loss - All the magnetic flux due to the primary coil does not pass through the secondary coil. So there is some leakage of flux. This loss can be minimized by winding primary over the secondary coil.
संबंधित प्रश्न
A series LCR circuit is connected to an ac source. Using the phasor diagram, derive the expression for the impedance of the circuit. Plot a graph to show the variation of current with frequency of the source, explaining the nature of its variation.
Derive an expression for the average power consumed in a series LCR circuit connected to a.c. source in which the phase difference between the voltage and the current in the circuit is Φ.
An LR circuit contains an inductor of 500 mH, a resistor of 25.0 Ω and an emf of 5.00 V in series. Find the potential difference across the resistor at t = (a) 20.0 ms, (b) 100 ms and (c) 1.00 s.
Consider the circuit shown in figure. (a) Find the current through the battery a long time after the switch S is closed. (b) Suppose the switch is again opened at t = 0. What is the time constant of the discharging circuit? (c) Find the current through the inductor after one time constant.
Answer the following question.
In a series LCR circuit connected across an ac source of variable frequency, obtain the expression for its impedance and draw a plot showing its variation with frequency of the ac source.
Using the phasor diagram, derive the expression for the current flowing in an ideal inductor connected to an a.c. source of voltage, v= vo sin ωt. Hence plot graphs showing the variation of (i) applied voltage and (ii) the current as a function of ωt.
In an LCR series a.c. circuit, the voltage across each of the components, L, C and R is 50V. The voltage across the LC combination will be ______.
In a series LCR circuit the voltage across an inductor, capacitor and resistor are 20 V, 20 V and 40 V respectively. The phase difference between the applied voltage and the current in the circuit is ______.
An alternating voltage of 220 V is applied across a device X. A current of 0.22 A flows in the circuit and it lags behind the applied voltage in phase by π/2 radian. When the same voltage is applied across another device Y, the current in the circuit remains the same and it is in phase with the applied voltage.
- Name the devices X and Y and,
- Calculate the current flowing in the circuit when the same voltage is applied across the series combination of X and Y.
Draw the phasor diagram for a series LRC circuit connected to an AC source.
