TRANSISTOR AS A SWITCH

DEAR STUDENTS,

PLEASE do this topic for pre board exam .


The transistor always remains in CUTOFF OR SATURATION MODE.In case of silicon the energy gap is 0.6 volt.If the transistor is in cut off mode the collector current is zero.When the input voltage is more than this value the transistor is in active mode & output voltage decreases as the contribution of ICRC INCREASES.tHE OUTPUT voltage decreases linearly till its value is less than about 1volt.After this the change becomes non linear & transistor goes to saturation mode.SO low input means OFF & HIGH INPUT MEANS ON.(REFER TO N.C.E.R.T PAGE 496)

ROTATIONAL MOTION ASSIGNMENT

Assignment of rotational motion (class 11)

Q.1 Why is the speed of whirl wind in a tornado alarmingly high?
(Use L = Iw)

Q.2 If Earth was to shrink suddenly to half its radius, what will happen to the length of the day?
(Use I=2/5Mr^2 and L=Iw)
Ans. Decreases

Q.3 When there is no external torque on the rotating body which of the following questions can change:-
1) Angular acc
2) Angular momentum
3) Angular Speed

Q.4 Equal torques are applied on a cylinder and a hollow sphere. Both have the same mass and radius. The cylinder rotates about its axis and the sphere about one of its diameters . which will acquire greater speed.
Torque=I*angular acc. Angular acc= torqe/I
Q.5 Asolid sphere is made to roll down from the same ht. on two inclined planes having having theta 2>theta 1. in which case will it take less time to reach the bottom?
Ans. In case of theta 2.

Q.6 The moment of inertia of 2 rotating bodies A&B are Ia & Ib (Ia>Ib)
And their angular momenta are equal. Which has greater k.i.?
Ans. B

Q.7 If the polar ice caps melts, how will it affect the duration of the day?
L=Iw=const.
Ans. L.w=2pie/T therefore, length of the day will increase.

resistance and resistivity

hey students this video is about resistance, resistors and resistivity

electricity and magnetism

hey students i am going to upload a awesome video on electricity and magnetism

electricity and magnetism

hey students i am going to post an awesome video on electricity and magnetism

electricity and magnetism

hey students i am going to give all of you a awesome video on electricity and magnetism

basic principles and working of cyclotron

hey student basic s ,i am going to post a beautiful video aboutprinciples and working of cyclotron

magnetic effects of current

DEAR STUDENTS OF CLASS 10
Here is an assignment based on comprehensive contMagnetic Effects of Current

Life skills

1.To illustrate the use of MAGNETISM in medicine a visit to a diagnostic centre where MRI (MAGNETIC RESONANCE IMAGING )
.is done. The students will meet the RADIOLOGIST to find
(a) the technology used in doing MRI
(b) The kind of organs in which MR imaging of the body is performed.

2.To visit the site where ALTERNATING CURRENT is generated & is sent through TRANSMISSION LINES. The ill effects of ELECTROMAGNETIC RADIATION associated with changing A.C.can be understood.

ACTIVITY BASED FORMATIVE ASSESSMENT

Activity 1
The wire AB is carrying current in downward direction as shown:-

A


A








A compass needle is first placed at pt.A & is taken to pt.B
Q1.What change in deflection is observed as the distance of compass needle is increased
From the wire.
Q2.For same position of compass needle the current in the wire is doubled. What change in the deflection is observed now?

Activity 2

Q1.A rod is carrying current in downward direction as shown in the diagram. It is placed in the uniform magnetic field as shown:








Answer the following questions
a) Give the direction of force experience by the rod.
b) State the rule which helps introducing the direction of force
c) How will the displacement of rod affected if the (i) Current in the rod is increased
(ii) Magnitude of magnetic field is
increased.
Q2. A selected shown in the diagram given below carries current as shown:







Mark the polarity at 2 ends.
Mark the region inside the solenoid where the field is uniform.
Complete the pattern.


Q3.In the diagram given below mark the arrows and complete the pattern (to depict the magnetic lines of force) Given the coil is perpendicular to plane of paper (a) what is the nature of magnetic field near the centre?
b) Which rule helps in drawing the direction of magnetic field lines?







Q4.In the diagram given below a coil is connected to a Galvanometer as shown:
A magnet is taken towards/ away from the coil explain the following observations:-

There is no deflection in the (G) when the magnet is stationary






The direction of deflection becomes opposite when the particular pole of the magnet is taken away instead of taken towards the coil.
Faster the motion greater is the deflection.



Match the following (For domestic electric in circuits

Or
Fill in the Blanks

Colour of Earth wire____________________Green

Colour of Neutral wire ____________________Black

Colour of live wire _____________________red

Two ratings of fire wire ____________5A, 15A

Connection to Earth provides a __________________lower resistance path


OR
Match the following

Earth Wire black

Neutral wire 5A, 15A

Electric rating green

livewire Geyser,airconditioner


Higher power rating appliances red
Lower power rating Healing effect of current

The fuse melts due to electric bulb, fan, electric ion

communication

Dear students

I want you to revise the following questions on communicationPHYSICS QUESTIONS

# Short answer type-

What are the three basic units of a communication system?
Ans- (i) Transmitter (ii) Communication channel
(iii) Receiver

Identify the parts X and Y in the following block diagram of a generalized communication system-
Ans- Part X is information source and Y is information channel/medium

What is the function of a transmitter antenna ?
Ans- To radiate power fed from transmitter into free space.

How does the effective power radiated by an antenna vary with wavelength ?
Ans- Power radiated by an antenna is inversely proportional to the square of the wavelength of the carrier wave.

What is the meaning of the term “attenuation” in communication system ?
Ans- Attenuation is the loss of strength of a signal while propagating through the medium.

Name three common types of wave propagation in space communication ?
Ans- (i) Ground wave (ii) Space waves or line of sight method
(iii) Sky waves

7. Why is ground wave transmission of signals restricted to a maximum frequency of 1500 kHz?
Ans- In ground wave propagation, attention increases with increase in frequency. For frequencies
above 1500 kHz the loss of power becomes extremely large. Hence, for ground wave
propagation, the upper frequency limit is 1500 kHz.

Define modulation index as referred to AM .
Ans- the modulation index of an AM wave is defined as ratio of the amplitudes of the modulating
Signal and the carrier wave.

What is the composition of amplitude modulated signal wave ?
Ans- The modulated signal consists of the carrier wave of angular frequency and side waves of angular frequencies.

What is Band pass filter ?
Ans- A band pass filter allows a band of frequencies to pass through and reject frequencies higher/lower than that band.

( SHORT ANSWER TYPE QUESTION- 2marks )

What is a communication system ? Draw a neat block diagram of a communication system.
What do you mean by point-to-point communication and broadcast ? Give examples too.
Write main advantages and disadvantages of AM technique.
Briefly explain why do we need a much higher bandwidth for a digital signal transmission than an analog signal.

( LONG ANSWER TYPE QUESTION )

1. Analytically explain the process of amplitude modulation. What is the frequency spectrum of AM signal ?
2. What is demodulation ? With the help of a circuit diagram explain the principle of a demodulator.
3. A TV tower has a height ‘h’. Derive the expression the maximum distance up to which signals can be received on earth.
4. A schematic arrangement for transmitting a message signal (20Hz to 20kHz) is given below-

n.Give two drawbacks from which this arrangement suffers. Describe briefly with the help of a block diagram the alternative arrangement for the transmission and reception of message signal.

project based learning

Dear students,
I wish you to see this power point presentation to see the effectiveness of PBL.
Project-based learning (PBL): best defined as instruction relating questions and technology relative to the student’s everyday lives to classroom projects. Students form their own investigation of their own group which allows students to develop valuable research skills. The students engage in design, problem solving, decision making, and investigative activities. It allows students to work in groups or by themselves and allows them to come up with ideas and realistic solutions or presentations. Students take a problem and apply it to a real life situation with these projects.

Q1. An electron alphaparticle,aproton have same kinetic energy.which one of these has the largest de-Broglie wavelength?
Q2. Why should the material used for making permanent magnets have high coercivity?
Q3.Distinguish between sinusoidal &pulse signal.
Q4 .In n-type silicon name the type of minority carriers &write the type of dopants.

Q5.Why is frequency modulation preffered over amplitude modulation for transmission of music.

Let us do something interesting

Dear students'Iwsh to give u one mark questions recently asked in board exams_

Q1. Unpolarised light is incident on a plane surface of glass of refractive index(mu) at an angle .If the reflected light gets totally polarised,write the relation between i & (mu)

Q2.Two nuclei have mass no. in the ratio1:3.What is the ratio of their nuclear density.

Q3.Draw a diagram to show refraction of a plane wavefront incident on a convex lens & hence draw refracted wavefront.

Q4.Magnetic lines can be entirely cofined with in the core of a Toroid ,but not with in a straight solenoid.why?

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FUNDAS OF ELECTROSTATICS

Questions on MAGNETIC EFFECTS OF CURRENT& MAGNETISM

Dear students
I am giving you important questions on MAGNETIC EFFECTS OF CURRENTS & MAGNETISM for rivison work.Class XII
Physics
Magnetic Effects of Current

. 1. A 0.5m long solenoid has 500 turns and has a flux density of 2.52 x 10-3 T at its centre. Find the current
in the solenoid.
2. A charged particle is moving in a perpendicular magnetic field. Derive the equation of path of charged
particle.
3. Give the construction, theory and working of a moving coil galvanometer.
4. The electron in the hydrogen atom circles round the proton with speed of 2.18 x 106 m/s in an orbit of
radius 5 x 10-10 m. What magnetic field does it produce at the proton?
5. A flat circular coil of 50 turns of max radius 25cms is in a fixed vertical place and has a current of 2A flowing through it. A small coil of 1cm2 area and having 100turns, is suspended at the centre of the circular coil in a vertical plane at an angel of 300 to that of the large coil. Calculate the torque that will act on small coil, when it carries that of the large coil. Calculate the torque that will act on small coil, when it carries a current of 1m A. What is the mutual inductance of the two coi
6. Find the value of resistance required to convert 0-5 m A into a voltmeter reading 0-10V. Resistance of
the millimeter is 2.5 ohms
7. Obtain an expression for the magnetic field at the centre of a square ofside 2a, carrying current I.
8. Derive an expression for the torque acting on a current carrying rectangular loop of wire placed in a
uniform magnetic field.
9. The protons are accelerated by a cyclotron, when a field of 2 wb m2 is
applied perpendicular to the plane of Dee. Calculate the energy of protons in Mev, if the circular part of
the protons has a radius of 0.4m before they leave the cyclotron.
1. Obtain expression for the magnetic field at the axial and equatorial point in case of a bar magnet. What are
neutral points?
2. Two iron bars are identical in appearance, one is a magnet and the other is not. How do you know which iswhich? You are not permitted to suspend the bars or use any other apparatus.
3. We find that more low energy cosmic rays reach the earth at the magnetic poles than at the magnetic equator? What could be the reason for this?
4. A 15 kV electron beam moving horizontally is subjected to horizontal magnetic field of 0.4 G normal to its initial direction. Estimate the radius of curvature of the path and up and down deflection of the beam over a distance of 0.3m.
5. Derive an expression for the torque acting on a magnetic dipole placed in a uniform magnetic field and hence define the magnetic moment of a dipole. Give the units of magnetic dipole.
6. Discuss the magnetism due to earth, which can be the possible cause of earth’s magnetism? Explain how the knowledge of elements of earth’s magnetism determines earth’s magnetic field completely.
7.. A neutral point is found on the prolongation of the axis of a bar magnet at a distance be 10cms from on end. If the length of the magnet be 10 cms and BH=0.3 G find the magnetic moment of the magnet.
8.Define coercivity and retentivity. How are soft iron and hard steel distinguished by the value of these quantities? Sketch the hysterisis loop for soft iron and hard steel. What do you infer about these materials from their hysterisis loops?
9.Write the relation for force between two parallel wires carrying current and hence define unit of current. 10. Find the flux density of the magnetic field to cause 62.5ev electron to move in a circular path of radius in 5cm given m = 9.1 x 10-31 kg, e = 1.6 x 10-19C.
11. Calculate the torque on a 50 turn circular look of radius 10cm, when placed with its place at 600 with a
magnetic field of 3.1 x 10-5T. The current through the coil is 2A.
12. To increase the current sensitivity of a moving coil galavanometer by 50%, its resistance is increased so that its new resistance becomes twice its initial resistance. By what factor does its voltage sensitivity change. 13.State Biot-Savart’s law. Using this law, obtain an expression for the magnetic field at a point situated on axis of a current carrying circular coil.

14.Two very long parallel wires A & B carry currents of 10A and 2A respectively and are at a distance of 20cm from each other. A third wire C of length 15cm and carrying a current of 10A is placed mid way between them. What is the magnitude and direction of force on wire C? The direction of current in all the three wire is the same

15. A long straight wire carries a current of 50A. An electron moving at 107m/sec is 5cm from the wire. Find the force acting on the electron if velocity is directed (i) towards the wire (2) parallel to the wire (iii) perpendicular to the directions defined by (i) and (ii)
16. Using Biot Savart LawFind an expression for the magnetic field due to straight current carrying conductor.

VIVA VOCE ON PRACTICAL CLASS12

Dear students,
I am giving you questions based on practicals class12
Test Based on Viva
Class XII

1. Define spherical aberration and draw diagram to show it in case of concave mirror.
2. What is parallax? How is it removed?
3. Define dispersion of light. Give its cause.
4. Show dispersion of white light into seven colours.
5. Define lateral displacements and give the factor on which it depends.
6. Define critical angle and deduce the relation between refractive index and critical angle.
7. Explain U-V graph in case of image formation in a convex lens.
8. Distinguish between primary and secondary cell. (give two differences)
9. How does rheostat act as a variable resistor, potential divider? (draw a diagram)
10. What a non inductive coil? Give one special feature of non inductive coil?
11. Draw neat and label diagram of leclanche cell.
12. Write chemical equation in Daniel cell.
13. Why is the emf of auxiliary battery greater than the emf to be measured?
14. Why are standard resistances made up of constantan and Manganin?
15. Define figure of merit and give it is S.I unit.

-------------------------------------------------------------------------------------------------------------------------------
Test Based on Viva
Class XII

1. Define spherical aberration and draw diagram to show it in case of concave mirror.
2. What is parallax? How is it removed?
3. Define dispersion of light. Give its cause.
4. Show dispersion of white light into seven colours.
5. Define lateral displacements and give the factor on which it depends.
6. Define critical angle and deduce the relation between refractive index and critical angle.
7. Explain U-V graph in case of image formation in a convex lens.
8. Distinguish between primary and secondary cell. (give two differences)
9. How does rheostat act as a variable resistor, potential divider? (draw a diagram)
10. What a non inductive coil? Give one special feature of non inductive coil?
11. Draw neat and label diagram of leclanche cell.
12. Write chemical equation in Daniel cell.
13. Why is the emf of auxiliary battery greater than the emf to be measured?
14. Why are standard resistances made up of constantan and Manganin?
15. Define figure of merit and give it is S.I unit.

moving charges&magnetism

Dear students I have made an impressive lesson on moving charges & magnetism.You can collcct
the CD of this lesson from senior physics lab.

to find equivalent capacity of the networks given below

Dear students

Find the eq. capacity of networks given and submit the answer-