# BCA 1st sem Physics paper 2019

GGSIPU, New Delhi | BCA | 1st Semester | Physics | 2019
• 1.a.

Define angle of repose and angle of friction.

Angel of Repose: Angle of repose of a granular material is the sleepiest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. Angle of Friction: The minimum angle of incline for which a body plac...
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• 1.b.

State Newton's 2nd law and derive the relation between force and momentum

Newtons's second law and relation between force and momentum: Newton's second law starts that "the acceleration of an object is dependent upon two variables - the net force acting upon the object and mass of the object" the acceleration is directly p...
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• 1.c.

State & prove Lemi's theorem Siat.

According to Lemi's theorem "if three forces acting at a point are in equilibrium, each force is proportional to the sin of the angle between the other two forces. Proving: Applying sin rule we got =P/Sin((180-$\alpha$))=Q/(sin(180-$\beta$))=R/(sin...
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• 1.d.
state and prove work energy theorem
The principal of work energy theorem states that the work done by the sum of all forces acting on a particle equals to the change in the kinetic energy of the particle. Proving: we know that $v^2=u^2+2as$ $v^2-u^2=2as$…………...
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• 1.e.

State and prove Gauss's theorem

GAUSS'S LAW: The net electric flux through any closed surface is equal to the net change (q) inside the surface divided by $\varepsilon_o$ $\phi_c=\frac {q}{\varepsilon_o}$ Proving: let us consider a change q in sphere of radius r, then $\overrighta... 2.5 • 1.f. Why two electric field lines cannot intersect each other Electric field lines always point in one direction at any point. When two lines intersect each other tangents are drawn at that point indicating two directions of electric field lines which is impossible therefore electric field lines cannot intersec... 2.5 • 1.g. Define Kirchhoff's first & second law (1) Kirchoff's current law states that current following into a node must be equal to current flowing out of it. (2) Kirchoff's voltage law or second law states tha for a closed loop series path the algebric sum of all the voltages around any closed... 2.5 • 1.h. State and explain Coulomb's law Coulomb's Law: The magnitude of the electric force between two stationary point charges in directly pr optional to the magnitude of their product and inversely proportional to the square of the distance between them.$F\propto \frac{q_1q_2}{r^2}$Pro... 2.5 • 1.i. What is Bohr's atomic model? Bohr's Atomic Model: According to bohr's atomic model, a small positive charged nucleus is surrounded by revolving negatively charged electrons in fixed orbits he concluded that electron will have more energy if it is located away from the nucleus wh... 2.5 • 1.j. What is doping of an intrinsic semiconductor? Name the charge carries in p-type semiconductors? DOPING: it is the process of adding impurities to intrinsic semiconductor to charge their properties. Charge Carrier in p-type Semiconductor: 1) Majority charge carriers are holes. 2) Majority charge carriers are electrons.... 2.5 • 2.a. What do you mean by barking of road? Calculate the angle of banking so that a vehicle of mass m can go with velocity v on a curved road of radius r without skidding. Banking of road is the process of raising out edges of a road over its inner edge through certain angle. A vehicle of mass 'm' moving with the velocity V on a curved road of radiue 'r'. Angle of banking is calculated by:$\tan Q$=$\frac{v^2}{rg}Q$... 5 • 2.b. b) Calculate the weight of a body of mass m placed in lift, when the lift: (i)Moves vertically upward with acceleration a. (ii)Moves vertically downward with acceleration a. (iii)Moves with constant velocity v. (iv) At rest. (1) Weight of a body of mass 'm' placed vertically upward with acceleration a. Body is moving upward having mass 'm' with acceleration 'a'. we can calculate by using formula =>R=m(g+1) (2) Weight of a body of mass 'm' placed in lift,vertically up... 7.5 • 3.a. What is meant by limiting friction? Explain the laws of friction. LIMITING FRICTION: The maximum friction that can be generated between two static surface in constant with each other is called limiting friction. LAWS OF FRICTION 1) when a body is moving, the friction is directly proportional to normal force and fri... 5 • 3.b. Two masses m1 & m2 are connected by a light string which passes over a friction less pulley such that mass m2 move vertically downward and m1 move vertically upward, calculate acceleration and tension in the string. Let there be two masses$m_1$and$m_2$when passes over a friction less pulley so, let$m_1$and$m_2$forming single system applying newton's second law.$(m_1+m_2)$a=F…………(1) let force applied on$m_1m_1$a=F-T&hellip... 7.5 • 4.a. Prove that total energy o falling freely body under gravity will remains same at all points on its path. Let a body of mass m falls from a point A. which is at height h from the ground A+A, Kinetic energy KE=) Potential energy = mgh total energy= 0 + mgh=mgh A+B,$V^2=U^2+2as$applying,$V^2=0+2gx$KE=$\frac{1}{2}mv^2$=$\frac{1}{2}m*2gx$=mgx PE=mg(h-x)... 5 • 4.b. b) Define conservative force. Prove that gravitational force is a conservative force. Also write the properties of conservative force. **Conservative Force:: It is a force with the property that the total work done in moving a particle between two points independent of the taken path. Gravitational Force is a conservative force Suppose we through a object of mass 'm' in upward direc... 7.5 • 5.a. What is Hooke's Law Calculate the Potential Energy of a spring when it is pulled to a displacement x from its mean position. Hooke's Law: It states that the force needed to extend or compress a spring by some distance scales linearly with respect to that distance, where 'K' is a constant factor of the spring. Potential Energy of a spring when it is pulled to displacement x... 5 • 5.b. by Show that when two bodies of equal masses suffer elastic collision in I-dimension, they will exchange their velocities. We know that for elastic collision:$e=\frac{v_2-v_1}{u_2-u_1}$in elastic collusion,${v_2-v_1}={u_2-u_1}v_2=v_1+u_2-u_1$…………(1) from conversion of linear momentum,$m_1u_1+m_2u_2=m_1v_1+m_2v_2$but mass are equal, 0 ... 7.5 • 6.a. Obtain the expression for capacitance of parallel plate capacitor with dielectric slab. Thickness of dielectric slab=t Outside of dielectric field=$E_0$Inside of dielectric field=$\frac{E_0}{K}$Where K is the dielectric constant. so, total potential will be: V=Et+$E_0(d-t)$V=$\frac{E_T}{K}$+$E_0(d-t)$V=$E_0(d-t+\frac{t}{k}$) we know... 5 • 6.b. Define electric field intensity. Calculate electric field intensity at any point on the axis of uniformly charged circular ring. Electric field Intensity:Electric field intensity E at any point surrounding the change q is defined as the force per unit positive change in the field. F=$q_0E$E=$\frac{F}{q_0}$Electric field of a uniformly charged ring: Consider a ring of radius ... 7.5 • 7.a. Find the total resistance when a number of resistances are connected in series and In parallel In Series: According to ohm's law we know that V=IR there are three resistance R1, R2, and R3 and I current is following V=IR V1=IR1 V2=IR2 V3=IR3 so, total voltage V=V1+V2+V3 IR=IR+IR2+IR3 R=R1+R2+R3 IN PARALLEL Here three resistance are connect... 5 • 7.b. Define Ohm's law. Explain the construction, working and principle & proof of wheat stone bridge with diagram in detail. Ohm's Law states that voltage or potential difference between two point is directly proportional to the current passing through the resistance and directly proportional to the resistance. V=IR Construction: A wheat stone bridge consist of four arms ... 7.5 • 8.a. Distinguish between Insulators, conductors and semi conductors in term of their energy band diagrams. 5 • 8.b. Explain briefly Rutherford's alpha scattering experiment and the atomic model based on the result of this experiment. Rutherford passed beam of$\propto$-particle through a thin gold foil to observe the atom and assumed how alpha particle scattered from the foil. 1) Most of the$\propto$-particle passed straight through a gold foil. 2) Some$\propto\$-particle were ...
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• 9.a.

What is p-n junction diode? Explain the action of forward bias

p-n junction diode is two terminal or two electrode semiconductor device, which allows the electric current in only one direction while blocks the electric current in opposite or reverse direction. When n-type semiconductor is joined with p-type sem...
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• 9.b.

What is transistor? Explain construction and working n-p-n & p-n-p transistor with diagram.

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is compound of semiconductor material usually with atleast three terminals for connections. n-p-n transistor Construction: The collector and...
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