Plus Two Physics Chapter Wise Previous Questions Chapter 7 Alternating Current is part of Kerala Plus Two Physics Chapter Wise Previous Questions and Answers Kerala. Here we have given Plus Two Physics Chapter Wise Questions and Answers Chapter 7 Alternating Current.
Kerala Plus Two Physics Chapter Wise Previous Questions and Answers Chapter 7 Alternating Current
The phasor diagram of the alternating voltage across an unknown device X and current flowing through it are shown below. [March-2018]
a. Identify the device X.
b. Draw the graphical variation of current and voltage with cot through this device.
c. Draw the phasor diagram which shows
the relation among VA, VL, VC and I in a series LCR circuit.
a. V and I are in phase.
X = R
Device is a resistror.
a. At resonance, in an LCR circuit, the emf and current are
ii. out of phase
iii. having a phase difference of y-
iv. having a phase difference of y
b. In the following circuit, find the value of V.
a. In a circuit carrying an ideal coil with negligible resistance, the power dissipated is …………
b. In the following circuit, find the impedance.
a. The core of a transformer has the following properties:
i. core is laminated.
ii. hysterisis loop is narrow.
Explain the significance of each property.
b. What is meant by resonance in an LCR circuit ? [March-2016]
a. i. For reducing eddy current. Eddy current heats the core and energy will be lost.
ii. For reducing hysteresis loss.
b. In LCR, at a particular frequency XL = XC. This condition is called resonance This frequency is called resonance
Transformers either increase or decrease AC voltage. [March-2015]
i. State the principle of a transformer.
ii. Explain with the help of a labelled diagram the working of a transformer.
iii. Explain briefly any three energy losses in a transformer.
i. Mutual induction.
ii. A transformer consists of a coil called the primary coil which is wound on a laminated soft iron core. Over the primary is wound another coil called the secondary coil. The AC to be stepped up or stepped down is applied between the ends of the primary.
An alternating current is produced in the primary. This creates an alternating magnetic flux which passes through the secondary coil. This produces an induced emf in the secondary and also a self induced emf in the primary.
a. Magnetic flux leakage: The total magnetic flux produced by the primary is not completely passing through the secondary. Thus there is a flux leakage. It can be reduced by using a closed core shaped to follow field lines.
b. Hysteresis loss: The core of the transformer undergoes a number of cycles of magnetisation and energy is lot due to hysteresis. It can be minimised by using material of low hysteresis like soft iron.
c. Eddy current loss (Iron loss): This current heats the core and energy lost. Reduced by using an insulated laminated core.
For many purposes, it is necessary to change an alternating voltage from one value to another. This is done with a transformer. [March-2014]
a. The basic principle behind a transformer………
b. Give an expression for the voltage and current in a transformer.
a. Mutual induction.
A fascinating behaviour of the series LCR circuit is the phenomenon of resonance. [March-2014]
a. Explain Resonance in an LCR circuit
b. Draw a graphical representation of variation of current amplitude with frequency.
c. What do you mean by sharpness of resonance? Explain it.
a. In LCR, at a particular frequency XL = XC. This condition is called resonance This frequency is called resonance
c. Sharpness of resonance is depends of quality factor or Q factor Q factor is equal to the ratio inductive reactance or capacitative reactance to the impedence at resonance.
impedence at resonce =R
When a capacitor is connected to an a.c source, it limits or regulates the current, but does not completely prevent the current.
a. Obtain the expression for current through an ac circuit containing capacitor only.
b. Write down the expression for capacitative reactance of a capacitor.
c. Hence explain why capacitors completely prevent current when it is connected to a dc source.
d. Name the current that exist between the plates of a capacitor.
e. What is the modification made by Maxwell in Ampere’s circuital theorem? [Model-2014]
Consider a circuit consisting of only capacitor connected to an alternating emf, E = Em sinωt
c. Reactance (resistance) of a capacitor inversely depends on the frequency. For dc, only one direction current will produce. So co is very less so very high resistance will produce hence it completely prevent current when it is connected to dc source.
d. Displacement current.
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