# NABTEB 2019 PHYSICS OBJ AND ESSAY VERIFIED ANSWER

**PHYSICS-Obj
1CDABCABBAB
11ABABAAACCD
21ACBDDCDDCD
31BDCDAACBAC
41BDACCABCDB**

**(1ai)
TABULATE
-WORK-
* Work is the product of force and perpendicular distance in the direction of the applied force.
* It is denoted by W.
* It is measured in Joule.**

-ENERGY-

* Energy is the capacity or ability to do work.

* It is denoted by E.

* It is measured in Joule.

-POWER-

* Power is the work done in a given period of time

* It is denoted by P.

* It is measured in watts or Joule per second( JS^-1)

(1aii)

The principle of conservative of energy states that in a closed system, energy can neither be created nor destroyed during a transformation.

(1aiii)

Diagram

(1bi)

Linear expansivity of solid (metal) is defined as the increase in length per unit rise in temperature. It is denoted by ? and measure in K^-1

(1bii)

diagram of a vacuum flask

* The vacuum flask is used to keep the temperature or quality of its content constant. If either hot or cold water is put in the flask , the temperature of the water will remain the same (constant) till the time of use. For this purpose ,the flask possess a soluble vessel together with silver and a vacuum between them. The stopper is made of an insulating material eg cork, wood. The flask regulation undergoes three main processes

– Cork

– Vacuum

– Silver wall

(1c)

Please use the Gamma sign in places written gamma

Gamma = 3?

Gamma = 3 * 4*10^-4

Gamma = 12*10^-4

Gamma = V – 4/4(120-20)

12 * 10^-4 = V – 4/4 *100

V = 4 +(12*10^-4 * 4*100)

V = 4.048cm

===================================

(2ai)

Acceleration of free fall due to gravity (g) : This is the concept of falling of an object, which explained that without air resistance, different object or mass release from rest at the same point will fall to the ground at the time(free fall). The given of this g=10ms^-2 approximately

(2aii)

(choose 2)

– Due to different altitude

– Due to different pole region

– Due to gravitational force magnitude

(2bi)

Moment of a force about a point : This is the product of the force and the perpendicular distance of its lines of action from the point. It is measured in Nm and is a vector quantity.

(2bii)

– The line of action of the forces must meet at a point

– The resultant must be zero

– The algebraic sum of components of the forces at any perpendicular direction is respectively zero

(2biii)

Tabulate

– Stable equilibrium : A body is said to be in a position of stable equilibrium when, on receiving a slight displacement it tends to return to its original state eg A cone resting on its base, a racing car ,a pendulum.

– Unstable equilibrium : A body is said to be in a position of unstable equilibrium when, on receiving a slight displacement it tends to move on farther away from its original position. eg A cone resting on its vertex, an egg standing at its pointed end

– Neutral equilibrium : A body is in neutral equilibrium when, on receiving a slight displacement it tends to come to rest in its new position. eg a cone resting on its curved surface, a ball or an orange rolling on a horizontal surface

(2ci)

Center of gravity of a body : This is defined as the point in which the resultant weight of a body appears to act, when the entire weight seems to be concentrated in a point where the resultant gravitational force on a body appears to act.

(2cii)

W * 10 = 35 * 10

W = 35 * 10/10

W = 35N

===================================

(3ai)

– Electric field : Is defined as any region where a charge experiences a force of experimental origin

– Electrical field intensity : Is defined as the force per Coulomb in a small charge particle placed at a point which does not influence the field.

E = Q/4?ER^2

(3aii)

Coulomb’s law : States that the force of attraction between two charged particles , Q and q is directly proportional to the product of their charges and inversely proportional to the square of their distance apart. ie

F ? Qq/R^2

F = KQq/R^2

K = 9 *10^9 Nm^2 C^-2

K = 1/4?Eo

(3bi)

Capacitor : A capacitor is a device for storing electrical charges. It consist of two conductors which are parallel to each other.

(3bii)

Capacitance of a capacitor : Capacitance of a capacitor is defined as the ratio of electrical charge to the potential difference (voltage) between or across the plates of a capacitor. It is denoted by C, measured in farad (F) and a scalar quantity ,thus charge in any plate is directly proportional to the potential difference across the capacitor.

(3biii)

– The capacitance of a parallel plate of a capacitor is directly proportional to the area ie C? A

– Parallel plates capacitor is inversely proportional to the the distance between the two plates. C ? 1/D

– The capacitance of a parallel plate capacitor in directly proportional to the dielectric constant relative permittivity capacitance ie C ? K

Hence area of plate, arrangement of the plate, dielectric constant and the distance of the plate apart affect capacitance of a capacitor

(3biv)

– A capacitor is used to separate A.C from D.C

– It is used to control current in an A.C

– Electrical charges or energy is stored in the capacitor

(3c)

C = 20*10^-6 F , V = 1500v , E =?

C=Q/V

Q=CV

Q= 20*10^-6 * 1500

Q=0.03C

**Energy is given as
E=1/2 Q^2/V
E=1/2CV^2
E= 1/2 * 20*10^-6 * (1500)^2
E=45J
===================================
COMPLETED!.
===================================**

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