0
Our database contains a total of 0 questions for physics Short Questions. You’ll prepare using this huge databank.
Question: 1
Answer: 1
152Electrostatic induction:
In the presence of a charged body an insulated conductors develops positive charge at one end and negative charge at the other end this process is called the electrostatic induction.
Experiment:
Consider a metallic sphere placed on an insulated stand. the sphere is neutral as it carries equal number of positive and negative charges now bring a negatively charged rubber road near the conducting sphere left part of the sphere that is closed to the rod becomes positively charged while the right part that is away from the rod becomes negatively charged. Negative charge in the rod repelas the negative charge of the sphere and shifts it to the opposite sign region of the sphere that is away from the rod .But as a whole the sphere is still neutral, since no charge has been added subtracted .Now if we remove the rod away from the sphere the charges again will spread uniformly on the whole surface of the sphere.
Question: 2
Answer: 2
252Given Data:
Q1= 10 uc
= 10*106c
Q2 5 uc
= 5*106c
R = 150cm =1.5m
K = 9109 Nm2C2
F=?
Solution:
As we know that:
F= k q1 q2/r
Putting values we get
F = (9*10/9) *510/6*10*10
(1.5)2
= 9*5*10/96 +16
2.25
= 45 *102
2.25
F= 0.2 N
Question: 3
Answer: 3
352Electric field:
The electric field of a charge is a region around a charge in which it exert electrostatic force on an other charge.
Explanation:
Consider a positive carge q and bring a test carge q/0 will experience a force .According to coulomb’s law the value of this force will depend upon the distance between two charges.
If charge q/0 is moved away from q this force will decrease till a certain distance the force would practically reduce to zero.
Electric field intensity:
The strength of electric field at any point in space is called electric field intensity .
Explanation:
If f is the force acting on test charge q/0 the electric field intensity would be,
F = f/q0
If the electric field due to a given arrangement of charge is known at same point, the force on any particle with charge q placed at that point can be calculated by using the formula,
F= qe …… This I force acting on a unit positive charge placed at that point.
Unit:
SI unit of electric field intensity is NC1
Quantity:
Electric intensity being a force is a vector.
Question: 4
Answer: 4
452Given Data:
C1 = 6uf
= 6*106f
C2 = 12UF
= 12*106F
V= 12 volt
Ce =?
V1 = ?
V2 = ?
Q1 = ?
Q2 = ?
Solution:
We know that,
1/Ce = I/C1+I/C2
I/Ce = I/6+ 1/12
= 2+1
12
= 3/12
1/Ce = 1/4
Ce =4uf
Ce = 4*106 f
Q = Cev
= 4*106*12
= 48*106
Q = 48uc
Zn series combination charge across each capacity is same so,
Q =Q1=Q2+V1 = Q1/C1
= 48*106/6*106
V1=8 volts
V2 = Q2/C2
= 48 *106/12*106
V2 = 4 volts.
Question: 5
Answer: 5
552Given Data:
C1 = 6uf
= 6*106f
C2 = 12UF
= 12*106F
V= 12 volt
Ce =?
V1 = ?
V2 = ?
Q1 = ?
Q2 = ?
Solution:
We know that,
1/Ce = I/C1+I/C2
I/Ce = I/6+ 1/12
= 2+1
12
= 3/12
1/Ce = 1/4
Ce =4uf
Ce = 4*106 f
Q = Cev
= 4*106*12
= 48*106
Q = 48uc
Zn series combination charge across each capacity is same so,
Q =Q1=Q2+V1 = Q1/C1
= 48*106/6*106
V1=8 volts
V2 = Q2/C2
= 48 *106/12*106
V2 = 4 volts.
Question: 6
Answer: 6
652In this combination capacitors are connected side by side i.e the right plate of one capacitors is connected to left plate of next capacitors.
Characteristics:
Each capacitor has the charge it battery supplies to charge to the left plate of the capacitor q., due to induction – Q charge is induced on its right plate i.e,
Q1=Q2=Q3=Q
The potential difference across each capacitor is different due to different value of capacitances.
The battery voltage has been divided among the various capacitors .Henc
= V1+V2+V3
Q=CV
V=Q/C
Q/C1+Q/C2+Q/C3
=Q ( I/C1 +I/C2+I/C 3)
Q= CV
V/Q =I/C
I/C= I/C1+I/C2+I/C3
Series combination of capacitors can be replaced with one equivalent capacitors having capacitance
= I/C1+I/C2+I/C3
If N capacitors are connected on series then
= I/C1 +I/C2+I/C3++I/Cn
Equivalent capacitance of a series combination of capacitors is smaller than any individual capacitance ,capacitors connected in series decrease the value of capacitance.
Question: 7
Answer: 7
752Given Data:
Q1= 500 uc
=500*106 C
Q2 = 100 uc
= 100*106 C
R =0.5m
K= 9*109 Nm2C2
F= ?
Calculations:
According to coulomb’s law,
F= k q1 q2/r
Putting values we get
= 9*109/500*106*100*106
(0.5)2
= 9*5*109102106102*106
(0.5) (0.5)
= 45*10/9+2+6+2+6
0.25
= 45*10
0.25
F = 1800 N
Question: 8
Answer: 8
852In the presence of a charged body an insulated conductor develops positive charges at one end and negative charges at their other end this process is called electrostatic induction.
Question: 9
Answer: 9
952The gold leaf electroscope is a sensitive instruments used for detecting and testing the nature of charges on a body.
Question: 10
Answer: 10
1052A device used for storing electric charge is called a capacitors the air or insulator placed between the plates of a capacitors is called dielectric.
Question: 11
Answer: 11
1152Charge is the basic property of the material body due to which it attracts or repels another body and there are two types of the charges one is positive and second I negative.
Question: 12
Answer: 12
1252The force of attraction or repulsion between two point charges is directly proportional to the product of the quantity of charges and inversely proportional to the square of the distance between them.
F= k q1 q2/r2
Question: 13
Answer: 13
1352A region around a charge in which it exerts electrostatic force on another charge.
Electric field intensity:
The force acting on a unit positive charge placed at a point its SI unit is NC1.
Question: 14
Answer: 14
1452If the distance between two charge is much greater as compared to their size then these bodies are considered as point charge.
Question: 15
Answer: 15
1552· Paper capacitors
· mica capacitors
· Parallel plate capacitor
· Electrolytic capacitors
Question: 16
Answer: 16
1652The direction of electric field of lines intensity in an electric field can also be represented by drawing lines these lines are known as electric field lines.
Question: 17
Answer: 17
1752The energy supplied by the unit charge as it moves from one point to the other in the direction of the field the unit of potential difference is volt.
Question: 18
Answer: 18
1852Electric potential at a point in an electric field is equal to the amount of work done in bringing a unit positive charge from infinity to that point its unit is volt or JC1
Question: 19
Answer: 19
1952It consist of two thin metal plates,parallel to each other separated by a very small distance the medium between the two plates is air or a sheet of some insulator this medium is known as dielectric.
Question: 20
Answer: 20
2052Each capacitor has the same charge across each capacitor in series combination if battery supplies +Q charge to the left plate of the capacitors CL,due to induction –‘Q’ cargeharge is induced on its right plate and +Q charge on the left plate of the capacitors i.e on each plate of capacitors charge is same.
Question: 21
Answer: 21
2152They are used for table fans, ceiling fans, coolers motors and washing machines they are used in electronic circuits of computers.
Question: 22
Answer: 22
2252The gold leaf electroscope is a sensitive instruments used for detecting and testing the nature of charges on a body.
Question: 23
Answer: 23
2352Fixed capacitors;
If the plates of the capacitors are immoveable then such capacitors are called fixed capacitors the capacitance of the such capacitor can not be changed.
Question: 24
Answer: 24
2452It is the ability of the capacitors to store charge when one coulomb of charge given to the plates of the capacitor produces a potential difference of one volt between the plates of the capacitor.
Question: 25
Answer: 25
2552The unit of capacitance is fared if one coulomb of charge given to the plates of a capacitor produces a potential difference of one volt between the plates of the capacitor then its capacitance would be one farad.
Question: 26
Answer: 26
2652The phenomenon of lightning occurs due to a large quantity of electric charge which build up in the heavy thunderclouds the thunder clouds are charged by friction between them water molecules in the thunderclouds and the air molecules.
Question: 27
Answer: 27
2752I/Ceq = I/C1 + I/C2 +I/C3
C1 C2 C3

K + V
Question: 28
Answer: 28
2852If a capacitor is connected to a battery of V, then the battery transfers a charge +Q from plate A to plate B so that –Q charge appears on plate B and +Q charge appears on plate A. The charge on each plate attract each other and thus remained bound with io the plate , in this way charge is stored in a capacitors for long time.
Question: 29
Answer: 29
2952The formula of parallel combination of capacitor is Ceq = C1+2+C3 +Cn
Question: 30
Answer: 30
3052Mica capacitor is an example of fixed capacitors Zn mica capacitor , mica is used as dielectric between the two metal plates mica is enclosed in a plastic case.
Question: 31
Answer: 31
3152The relation between electric potential and potential energy is given by V = W/q.
Question: 32
Answer: 32
3252We have learnt already that an inherent property of an
object is its mass. An object with smaller mass will have less inertia as
compared to an object with larger mass. Along with mass, another inherent
property of an object is its electrical charge. Charge is measured in units of
coulomb ©
There are two kinds of charges:
A simple experiment
can be performed to show that there are two types of charges, one type is
called positive and the other negative.
There are two types of charges and similar charges repel and
different charges attract.
Interestingly it is seen that after rubbing the silk cloth
and animal fur also acquired the charge in opposite sense to glass rod and
rubber rod respectively. `Structure of Atom’ we learnt that all matter is made
up of atoms. Atoms have two kinds of charges: protons contained in the nucleus
of atom have positive charge, whereas electrons clouding around the nucleus
carry negative charge, neutrons inside the nucleus have no charge. The charge
on an electron or proton is said to be an elementary or fundamental charge
because all known charges are made up of electrons and protons and so all
charges are integer multiples of the fundamental charge.
As all the matter is
made of atoms, thus every material object has charges in it. We often do not
notice the effects of electrical charges because most objects have the same
number of electrons and protons in them (therefore we have equal and opposite charges)
and as a result the net effect is zero and so these objects are electrically
neutral
Electrification:
Electric charge
is not created in the process of charging object, charges are only transferred
between the objects. In electrification experiments It is seen that silk
cloth/animal fur also attained charge. Thus, in those experiments, charge was
not produced rather it was only transferred and we can say that objects can be
charged by removal or addition of charges (specifically electrons) called electrification.
Question: 33
Answer: 33
3352A change in distribution of electrical charge in an object,
caused by the influence of nearby charges is called electrostatic induction.
This effect may be shown by bringing a negatively charged rubber strip near to
an insulated metal sphere X which is touching a similar sphere Y. Electrons in
the spheres are repelled to the far side of Y.
Question: 34
Answer: 34
3452Electroscope is a device used for detecting and testing the
nature of charge on a body. It works on the principle that similar charges
repel each other.
A simple form of electroscope consists of a metal bar which
has a metallic sphere (ball) at its upper end. Thin flexible metal leaf ( made
of gold, silver, copper or any other metal ) is attached to the lower end of
metal bar.
The lower part is enclosed in an insulated housing.
Working:
In order to
detect charge on a body we touch the metal ball with it. For example, if we
touch it with negatively charged rubber rod some of its excess electrons will
be transferred to the ball and then they will spread throughout the metal rod
and the metal foil. The flexible metal leaf will be repelled by the similar
change on the metal rod and will move away from the rod by rising higher , As
more electrons are transferred to the electroscope, the metal leaf will rise
higher, Alternatively if the rod id positively charged it will attract
electrons from the electrons from the electroscope, leaving a net positive
charge on it. Once again the foil will rise.
However to test the nature of charge on the body we charge
the electroscope with some known charge first. Now if the same charge is added
to the metal ball, it will increase divergence of flexible metal leaf and
opposite charge will decrease the divergence allowing us to identify the
unknown charge on the body
Question: 35
Answer: 35
3552Coulomb's lawstates that: The magnitude of the
electrostatic force of attraction or repulsion between two point chargesisdirectly
proportional to the product of the magnitudes of charges and inversely
proportional to the square of the distance between them. The forceisalong
the straight line joining them
Statement: The electric force between two stationary point
charges is directly proportional to the product of the charges; inversely
proportional to the square of the distance between them and is directed along
the line joining these charges.
The attraction of an uncharged object by a charged object
near it is due to electrostatic induction. For example, it is the reason for
the opening question `why after running a plastic comb through our hair on a
dry day does the comb attract small pieces of paper?’. The influence of the
charge on the comb redistributes the charges in the paper due to electrostatic
induction.
Charges in the pieces of paper with the same sign (polarity)
are pushed away while charges with opposite sign are pulled closer. Thus change
in distance means the attractive force due to the closer opposite sign charges
is greater than the repulsion due to the same sign charges which have been
pushed further away. As coulomb forces decreases as distance between similar
charges is increased, on the other hand it increases for dissimilar charges, as
a result it overcomes inertia and lifts small pieces of paper. This creates a
net attractive force which pulls the paper towards the comb.
Question: 36
Answer: 36
3652Electric Field and Its Intensity:
The region around a
charge in which an electric test charge would experience an electric force is
called electric field, And the strength a of the field (equal to the force
experience by a (+1C) test charge) at any point is called electric field intensity.
An electric field exist in the region of space around a
charged object in three dimensions. When another charged object enters this
electric field, an electric forcer acts on it even without any physical contact
between the charges.
Consider a small positive test charge q_{o} near the
greater magnitude charge q Now the electric field E at any point in space is
defined as the force F acting on unit positive charges q_{o} , divided
by the magnitude of the test charge q_{o} , mathematically
E =F_{E}/q_{o} equation (1)
Equation (1) gives the mathematical form of electric field intensity.
The SI unit of electric field intensity is newton per coulomb (NC). It is a
vector quantity having direction in which a positive test charge would move
under the influence of force.
An easy way to visualize an electric field is to draw lines
that follow the same direction as the electric field intensity vector E at any
point. These lines are called electric field lines.
Electric field intensity vectors help to visualize the
electric field. Electric field lines are a kind of “map” That gives the
direction and strength of the field at various places. The direction of the
lines is radially outward for a positive charge and radially inward for a
negative charge.
Question: 37
Answer: 37
3752Electric Potential:
The electric
potential energy `U’ per unit charge `q’ in an electric field is called
electric potential V
V= U/q= W/q Equation (1)
The electric potential units of joules per coulomb (J C), or
volt. (V) in honor of Italian scientist Alessandro Volta. The potential at a
point is one bolt, when it requires one joule of work to move a positive charge
of one coulomb form a point of ZERO potential
to that point.
1volt = 1joule/1coulomb
The concept of electric potential is closely related to
electric field. Electric field is the force per unit charge, whereas the
electric potential is the energy per unit charge. However electric potential is a scalar quantity, since, it is easier to
solve problems with scalars, therefore, and it is simpler to solve problems
with electric potential rather than electric field.
Let us consider a positive charge +q is placed in an electric
field at point B. If the charge is allowed to move freely, it will acquire
kinetic energy and will move from B to A. Conversely, we can say that an
external force is required to keep the charge at rest or to move with uniform
velocity from A to B Thus
V_{B} – V_{A} = W_{AB}/q equation (2)
Often point A is taken to be at infinity , meaning a large
distance from the charges that produce the electric field, and the electric
potential at A is taken to be zero.
Note that the choice of zero potential at infinity is taken
arbitrarily and for simplicity, such that
V =
W/q equation (3)
In equation (3) V (by
definition) the Work that must be done against the Electric Field to bring a
test charge q from infinity to a specific location.
Question: 38
Answer: 38
3852Capacitor is a device used for storing charge, it consists
of two conductors separated form (without touching) each other, carrying
charges of equal magnitude but opposite sign.
The basic elements of any capacitor two isolated conductors (having
charge +Q and  Q) of any shape. No matter what their geometry, flat or not, we
call these conductors plats, each capacitor plate carries a charge of the same
magnitude, one positive and the other negative. Due to the charge the electric
potential of the positive plate exceeds that of the negative plate by an amount
V.
The insulating medium that separates the plates of capacitor
(air or some other insulating material) is referred to as dielectric
Capacitance of capacitor:
The capacitance C
of a capacitor, is the ratio of the
magnitude of the charge on either
conductor, is the ratio of the magnitude of the charge on either conductor to
the magnitude of the potential difference between them.
When charge Q is increased on the plates of the capacitor
the potential difference V also increases and vice versa
Q V or Q =CV
Where C is the constant of
proportionality and is called the capacitance of a capacitor
Therefore C= Q/V eq
(1)
The capacitance of capacitor is the
amount of charge the capacitor can store per unit of potential difference . The
capacitance of a capacitor depends upon the size and shape of the plates. Its
also depends upon the separation and nature of insulating material in between
the plates.
Unit of Capacitance:
The SI Unit of capacitance is coulombs
per volt or the farad (F), named in honor of Micheal Fraday, such that
1F = 1C/C
The farad is a very large unit of
capacitance. In practice, typical devices have capacitances ranging from
microfarads 10^{6} F). For practical purposes, capacitors often are
labeled “µF” for microfarads and “pF” for Picofarads.
Question: 39
Answer: 39
3952Question: 40
Answer: 40
4052Question: 41
Answer: 41
4152Question: 42
Answer: 42
4252 Medium between two charges
 system of unit in which F, q and r are measured
 The permittivity of free space
Question: 43
Answer: 43
4352Question: 44
Answer: 44
4452 The electric field intensity is tangent to the electric field lines at each point.
 The number of lines per unit area through a surface perpendicular to the lines is proportional to the electric field strength in a given region.
 Electric field is strong when the field lines are close together and weak when the lines are far apart.
 No tow field lines cross each other.
Question: 45
Answer: 45
4552Question: 46
Answer: 46
4652Question: 47
Answer: 47
4752Question: 48
Answer: 48
4852Question: 49
Answer: 49
4952Question: 50
Answer: 50
5052Question: 51
Answer: 51
5152 Photocopying
 Car painting
 Extracting dust from dirty carpets
 Extraction dust from chimneys of industrial machinery