ELECTROSTATICS

Unit 13

ELECTROSTATICS

Q.1 what’s meant by natural philosophy or static electricity?.

Ans. natural philosophy

The study of charges at rest is termed natural philosophy.

Q.2. however are you able to show by straightforward experiments that there ar 2 varieties of electrical charges.

Ans. A comb rubbed with hair and amber rubbed with silk attract little items of paper. this is often thanks to electrical charges, they acquire throughout rubbing.

The following experiments show that we are able to manufacture 2 varieties of electrical charges through the method of rubbing.

Experiment 1: Take a plastic rod. Rub it with fur and

suspend it horizontally by a silk thread. currently take another plastic rod and rub it with fur and convey close to the suspended rod. can|we’ll|we are going to} observe that each the rods will repel one another (Fig. 13.1). It suggests that throughout the method of rubbing each the rods were charged.

Experiment 2: currently take a glass rod and rub it with silk and suspend it horizontally. once we bring the plastic rod rubbed with fur close to the suspended glass rod, we have a tendency to observe that each the rods attract one another (Fig. 13.2).

In the initial experiment, each rods ar of plastic and each of them are rubbed with fur. Therefore, we have a tendency to assume that charge on each rods would be of an equivalent kind. *

In the second experiment, rods ar not like and their attraction implies that charge on the 2 rods aren’t of an equivalent kind however of opposite nature.

Q.3. what’s meant by electricity induction? what’s the tactic of , charging bodies by electricity induction?

Ans. electricity INDUCTION

The process of charging a conductor with none contact with the charging body is understood as electricity induction.

Method of Charging Bodies by electricity Induction

Take 2 metal spheres A associated B and place them on an insulating stand as shown in Fig.13.3 (a). currently bring a charged rod close to sphere A as shown in Fig. 13.3(b). The rod can attract charge towards it and repel charge faraway from it. charge are developed on the left surface of the sphere A that is on the point of the rod. whereas charge are developed on the correct surface of the sphere B.

(d) (e) Fig/l three.3: Charging 2 spheres by electricity induction.

Now separate the spheres by atiny low distance whereas the rod remains close to the sphere A. the 2 spheres are oppositely charged and attract one another as shown in Fig.13.3 (c). take away the rod. the costs on spheres set up themselves as shown in Fig.13.3 (d). currently separate the spheres by an oversized distance.

In this method, associate equal and opposite charge are developed on every metal sphere. this is often charging by electricity induction.

Q.4. however will electricity induction dissent from charging by friction?

Ans. throughout the method of charging by friction, we have a tendency to rub a neutral body with another neutral body. however within the method of electricity induction, we have a tendency to charge a conductor while not creating any contact with the charging body.

Q.5. what’s a gold foil electroscope? Discuss* its rule with a label diagram.

Ans. measuring device

A gold foil measuring device could be a sensitive instrument used for police work charges.

Working Principle

It accommodates a brass rod with a brass disk at the highest and 2 skinny leaves of foil hanging at rock bottom. The rod passes through associate nonconductor that keeps the rod in situ and conjointly retains the costs. Charges will move freely from the disk to the leaves through the rod. a skinny foil is hooked up on the lower portion of the within of the jar. Usually, the foil is .grounded by connecting a copper wire. This protects the leaves from the external electrical disturbances.

Q.6. Suppose you have got a glass rod that becomes charged once you rub it with wood. Describe however would you charge the measuring device,

(i) negatively

(ii) absolutely

Ans. CHARGING THE measuring device NEGATIVELY

In order to vary the measuring device negatively, bring a charged rod close to the disk of the measuring device. charge can seem on the disk of the measuring device whereas positive charges can shift to the leaves. currently connect the disk of measuring device to the earthed foil by a conductor. Charge of the leaves can flow to the world through the wire. currently if we have a tendency to initial break the world affiliation so take away the rod, the measuring device are left with charge.

connection so take away the rod, the measuring device are left with charge.

CHARGING THE measuring device absolutely

In order to charge the measuring device absolutely, bit the disk of measuring device with the charged glass rod. The charge of the rod are neutralised as some electrons from the disk are shifted to the glass rod deed the disk with way over positive charges. currently take away the glass rod from the disk, measuring device can become charged.

Q.7. With the assistance of measuring device however you’ll be able to notice the presence of charge on the body?

Ans. police work THE PRESENCE OF CHARGE

In order to observe the presence of charge on anybody, bring the body hear the disk of associate uncharged measuring device. If the body is neutral, there’ll be no deflection of the leaves (Fig.13.5-a). however if the body is absolutely or charged, the leaves of the measuring device diverge. as an example, if the body is charged then thanks to electricity induction charge can seem on the disk whereas charge can seem on the leaves (Fig.13.5rb). The leaves of measuring device repel one another and diverge as a result of every leave gets similar charge. The ‘divergence of leaves can rely on the quantity of charge.

Q.8. Describe however you’d confirm the character of the charge on a body by mistreatment measuring device.

Ans. police work the kind OF CHARGE

For the detection of sort of charge on a body, measuring device is initial charged either absolutely or negatively. Suppose the measuring device is charged. currently in ordjBjr to observe the kind of charge on a body, bring the charged body close to the disk of the charged measuring device. If the divergence of the leaves will increase.

Q.9. Describe however you’d distinguish between conductors and insulators with the assistance of measuring device.

Ans. measuring device may be wont to distinguish between ‘ insulators and conductors. bit the disk of a charged measuring device with the fabric beneath take a look at. If the leaves collapse from their diverged position, the body would be an honest conductor. If there’s no amendment within the divergence of the leaves, the body is associate nonconductor.

Q.10. justify law of natural philosophy and write its mathematical kind.

Ans. law

It states that,

The force of attraction Or repulsion between 2 purpose charges /s directly proportional to the merchandise of the costs and reciprocally proportional to the sq. of the space between them.

i.e. Focqiq2

and Foc-j ”

Combining equivalent weight. (i) and (ii), we get

(in)

where F is that the force between the 2 charges and is termed the Coulomb’s force, q, and q2 ar the 2 charges and r is that the distance between the centres of the 2 charges, k is that the constant of proportion and is capable

k=

The value of k depends upon the medium between the 2 charges and also the system of units within which F, letter and r ar measured, e0 is that the permitivity of free house.

Now if the medium between the 2 charges is air, then the worth of k in SI units are nine x 109 Nm2C~2.

Q.11. what’s going to happen to the Coulomb’s force, if the space between the 2 purpose charges is

(i) doubled

(ii) halved

Ans. in line with law

i F = k

‘2 The Coulomb’s force is reciprocally proportional to the sq. of the space between them, thus

(i) if we have a tendency to double the space, the Coulomb’s force can cut back to at least one fourth.

(ii) if we have a tendency to cut back the space to [*fr1], the Coulomb’s force can become fourfold.

Q.12. within which direction will Coulomb’s force act between the 2 charges?

Ans. The Coulomb’s forces perpetually act on the road connection the 2 purpose charges. These have equal magnitudes however perpetually act in opposite directions.

Q.13. what’s meant by field and electrical intensity?

Ans. field

” a district around a charge within which it exerts electricity force on another charge is understood as field.

ELECTRIC INTENSITY

The strength {of electrical|of electrical} field at any purpose in house is understood as electric intensity.

Q.14. is electrical intensity a vector quantity? what’s going to be its direction?

Ans. electrical intensity being a force could be a vector amount. Its direction is that the same as that of the force performing on the positive take a look at charge. If the take a look at charge is liberated to move, it’ll perpetually move within the direction of electrical intensity.

Q.15. notice the electrical intensity thanks to a degree charge letter.

Ans. so as to seek out the worth of electrical intensity at a degree within the field, of charge +q, we have a tendency to place a take a look at charge q0 at that time (Fig. 13.7). If F is that the force performing on the take a look at charge q0, the electrical intensity would incline by

q° Thus, field intensity at any purpose is outlined as:

The force performing on a unit charge placed at that time is understood as field intensity.

Unit: The SI unit of electrical intensity is newton per coulomb (NC~r).

If the electrical field thanks to a given charge is understood at some purpose, the force on any particle with charge letter placed at that time is calculated by mistreatment the formula: .

F = qE

Q.16. what’s meant by purpose charges?

Ans. purpose CHARGES

If the space between the 2 charged bodies is far bigger as compared to their size, the bodies ar thought of to be purpose, charges.

Q.17. what’s meant by field lines or electrical lines of force. however will we have a tendency to draw the electrical field lines.

Ans. field LINES

The direction of electrical intensity in an electrical field is indicated by drawing lines.These lines ar called field lines or electrical lines for force.

Electric lines of force ar notional lines around a field charge with associate arrow head indicating the direction of force. field lines perpetually moves from charge towards the charge. It suggests that electrical lines of force originate from a charge and terminate at a charge. The spacing between the electrical lines of force shows the strength of the electrical field.

Q.18.How ar electrical lines of force associated with the electrical field intensity?

Ans. electrical lines of force ar associated with the electrical intensity in any region of house within the following way:

1.The electric intensity is tangent to the electrical field lines at every purpose

The number of electrical lines.of force per unit space through a surface perpendicular to the Knes is proportional to the electrical strength in an exceedingly given region (Fig. 13.9-b). .

The electric field is powerful once the electrical lines of force ar close and weak once the electrical lines of force ar so much apart. electrical lines of force ne’er cross one another.

Q.19. however do the electrical field lines for associate isolated positive and charge ar drawn?

Ans. the electrical field liens for associate isolated positive and negative purpose charge ar shown below

Q.20. however would you outline voltage between 2 points? outline its unit.

Ans. voltage

The voltage between 2 purposes is that the energy provided by a unit charge as its moves kind one point to the opposite.

Unit: The SI unit of voltage is V (V), that is capable joule per coulomb (JC~1).Volt

If one joule of labor is completed against field in delivery one coulomb charge from eternity to a degree within the field then the potential at the purpose vjii be one V.

Q.21. what’s meant by lepton volt?

Ans. eV

It is a smaller unit of energy and is outlined as:

“The quantity of energy provided by associate lepton because it moves between 2 points having a possible distinction of 1 V.

1eV=1.6×1(T19J

Q.22. Show that voltage is delineate as energy transfer per unit charge between the 2 points.

Ans. If W is that the work wiped out moving a unit charge letter from eternity to a degree within the field, the electrical potential V at this time would incline by

where the work done W is capable the energy provided. once a charge is discharged in an electrical field, It moves from a degree of upper potential say A to a degree at lower potential say B. If the potential of purpose A is Va which of purpose B is Vb, the potential

energy of the charge at these points are qVa and qVb severally.

The amendment in P.E. of the costs once it moves from purpose A to B are capable qVa – qVb. This energy is employed in performing some helpful work. Thus

Energy provided by the charge = q(Va – Vb)

If letter is capable one unit, then the voltage between 2 points becomes capable the energy provided by the charge. therefore we have a tendency to outline voltage between 2 points as:

The energy provided by a unit charge because it moves from one purpose to the opposite within the direction of the sector.

Q.23. what’s distinction between potential and potential difference?

Ans. the electrical potential at any purpose within the field is that the P.E. of a unit charge placed at that time. that is capable the quantity of labor wiped out delivery unit charge kind eternity thereto purpose. Whereas the voltage between 2 purposes is that the energy provided by a unit charge because it moves from one point to the opposite.

Q.24. what’s distinction between gravitative potential and electrical potential?

Ans. The gravitative potential at a degree within the gravitation field is that the gravitative P.E. of a unit mass placed at that time. Whereas the electrical potential at any purpose within the field is that the potential energy of a unit charge placed at that time.

Q.25. A’capacitor could be a energy storing device. Discuss.

Ans. CAPACITOR

A device wont to store charge is understood as electrical condenser.

A electrical condenser consists of 2 skinny metal plates, parallel to every alternative separated by a awfully little distance. The medium between the 2 plates is air or a sheet of some nonconductor. This medium is understood as nonconductor.

If +Q quantity of charge is given to plate A of a parallel plate electrical condenser, thanks to electricity induction, it might induce -Q charge on the inner surface of the plate B and +Q on its outer surface. The lines provide between the plates are shown within the figure. ,

There exists a force of attraction between the charge +Q keep on the plate A and also the charge -Q elicited on the inner surface of plate B. thanks to this force of attraction, the costs ar sure among the plates and remained keep for an extended amount.

Q.26. What does one mean by capacitance of a capacitor? outline the unit of. CAPACITANCE

CAPACITANCE

The ability of a electrical condenser to store charge is understood as capacitance.

Due to presence of the costs on the plates, a possible distinction V is etovetoped across them that is directly proportional to the charge letter deposited on the plate A.

i.e. letter « V or letter « CV wherever C is that the constant of proportion, referred to as the capacitance of the electrical condenser.

.or C = V The capacitance of the electrical condenser is outlined as:

It is a magnitude relation between the charge and also the voltage applied across the plates of the electrical condenser.

Unit: The SI unit of capacitance is F (F).