10th Class Chapter 5 Physics Long Questions

Series combination;

In series combination resistance are connected end to end and electric current has a single path through the circuits.

Equivalent resistance of series cicvit;

The total vottage in a series circuit divides among the individuals resistance so the sum of the vottage across the resistanceof each individual resistance is equal to the total vottage supplied by the source thus we can write as :

V=V1-V2+V3m (1.4.6)

Where v is the vottage in across the saltery and V1,V2,V3 are the vottage across resistance R1,R2 and R3 resIpectively

V=IR1+IR2+IR3V

V= I(R1+R2+R3)R

We can replace the R1,R2,R3+m+Rn

Given data:

V=220v

P=100w

T=5*30=150hours

R=?

Solution:

P=V1

I=V/R

P=V2/R

R=V2/P=(220)2/100

= 220*220/100

= 48452

Energy in Kwh = watt/100*time

=100/1000*150

= 15 kwh

Specific Resistance:

The resistance of one meter cube of a ubstance is called its specific resistance or resistivity it is represented by p.The unit of specific resistance (P) IN OHM meter πm.

At a centain temperature and for a particular substance the resistance R depends at the length of wire

Length of wire:

The resistance R of the wire is directly proportional to length of the wire it resistance will also be doubled and it its length is halved its resistance would become one hall.

Cross sectional area of wire:

The resistance R of the wire is inversely proportional to the area of cross sector A of the wire.

R*I/A =(2)

It means that a thick wire would have smaller resistance than a thin wire,

R *I/A R= P L/A------(4)

From eq (3)

P= R*A/L-----(4)

If we put L=Im and A= Im2 then eq 140

P=R

Given data:

Length of wire L=Im

Diameter of the wire d=2m=2*10-3m

Cross sectional area of th wire

A=πd2/4= 3.14*(2*10-3)2 m2/4

A= 3.14*10-6 m2

Specific resistance of copper =1.69*10-3

R= P*L/A= 1.69*10-8 lm *1m (3.14*10-6 m2

R= 0.54*10-2 π = 5.4*10-3 π

Ohm’s law is stated as the amount of current I passing through a conductor is the proportional to the potential difference V applied across its end provided the temperature and physical state of the conductor does not change mathematically,

I *V (OR) VAT OR V=IR

Where R is the constant of proportionality and is the resistance of conductor.

Limitations of Ohm’s law

Ohm’s law is applicable when temperature and physical state of conductor does not change.

Solution:

R = 10M π

=10 *10-6 π

V= 100 V

I=?

V= IR

I = V/R

=100/10*106

=10/10-3, 10+3

=10*10-3/1000

=0.01*10-3 A

=0.01mA

The rate of flow of electric charge through any cross sectional area is called current

I = Q/

Current flowing from positive to negative terminal of a battery due to the flow of positive charges is called conventional current.

Potential differenc across the two ends of a conductor causes the dissipation of olectrical energy into other forms of energy as charge flow through the circuit e.m.f it is the energy supplied by a battery to a unit positive charge when it flows through the closed circuit.

The amount of current passing through a conductor is directly proportional to the potential difference applied across the provided the temperature and the physical state at a conductor does not change.

V= IR

Conductor one materials through which electricity passes easily

Insulator:

The substance which do not allow to conduct heat and electric current.

The property of a substance which offers opposition to the flow of current through it is called resistance

Unit of resistance : ohm

1 Kwh = 3.6 (H)

3.6*10-3 *10,3 j = Ikwh

1000j = 1/3.6*10,3 kwh = I kwh/3.6*k =1.36 wh – 0.28

If voltmeter is connected in parallel then due to high resistance it will not effect the current in circuit due to which voltage of circuit will be different across different resistance.

If a coil is rotated in a magnetic field a current will be induced in the coil the current that does not charge its direction of flow and is unidirectional is known as direct current.

State joule’s law:

The amount of heat generated in a resistance due to the flow of charges isd equal to the product of square of current I resistance R and his time duration.

No, current in any circuit can’t flow without potential difference between ends of boltary according to ohm’s law current passing through the conductor is directly proportional to potential difference.

The other wire is maintained at zero potential by connecting it to the earth at the power station itself and is called neutral wire (N).

Diamond is an insulator because it has a very wide band gap and therefore would not have any free electrons to conduct.

If one colomb of charge passes through any cross section in one second then current will be equal to one ampere.

Ideal galvonameter should have very small resistance to pass the maximum current in the circuit after

In order to measure e.m.f of the battery we connect voltmeter directly with the temperature of the battery.

A short piece of metal that melts when excessive current passes through it.

Circuit breaker:

A switch that automatically interrupts the current of an overloaded electric current.

If its length is halved then its resistance would become one half.

Galvanometer is converted into an voltmeter by connecting a suitable high resistance in series with the galvanometer.

Always use fuse for safety measures in household circuit.

Always use earth wire with these appliances whose casing is made up of metals.

Electric power:

Electric power is the rate at which electric energy is transferred electric power is measured by capacity and is commonly expressed in megawalts

Kilowatt hour:

Kilowatt hour isa watt of energy equaivalent to kilowatt (1kw) of power expended for one hour of time.

Diamond is not a good conductor of electricity because there are no free electrons flowing around in the structure of the diamond.

Advantages are that you can add more power sources like batteries and increase the force of the out which grants you more power.

Parallel circuit:

In a parallel circuits all the external resistors are supplied the same potential difference which is not possible in a series circuit.

An earth wire is a wire that goes into the ground to diperse with electricity that excess electricity goes through to prevent a circuit from frying itself.

Electric Current:

`Time rate of flow of charge is called current’.

A charge `Q’ flowing through any cross-sectional area in time `t’, corresponds to a current I that is defined mathematically as

I = Q/t Eq (1)

When charges flow, they can be positive, negative or both. For example the current in metals is due to flow of negatively charged electrons. The current in the beam of a particle accelerator is due to positively charged protons, while in some cases such as gases and electrolytes, the current is due to the flow of both positive and negative charges. Moving charges, whether positive of negative, are referred to as charge carriers. The total current is I=I.+I.

The SI unit of current is ampere and is represented by capital letter A. When one coulomb charge flows through any cross-sectional area in one second, the current is one ampere

1 A = 1 C/s.

Since coulomb is large amount of charge, therefore ampere is also a large unit of current. In real life situations, we deal with small values of current like mille amperes (mA =10^-6 A)

Conventional flow of current:

The direction of conventional current is the direction in which positive charges flow.

In conductors (e.g. metals), the actual flow of current is due to electrons which flow form negative terminal to the positive terminal of battery. However, before the discovery of electron, the current was assumed to flow from positive to negative terminal of the battery even for conductors. This assumed direction of current flow is now called conventional current.

Potential Difference and EMF:

The electric potential at one point can be higher, lower or equal to the potential difference at other point. ` The difference of electric potential between two points is called potential difference’.

For example in an electric circuit which has an electric device (electric bulb) connected across a battery through conducting wires. The charge leaving the positive terminal of the battery has potential energy in device; part of this energy is lost (concerted to other forms of energy). Thus, there is a difference of potential energy per coulomb of charge (q) from once side of the electric device to the other, which is termed as potential difference.

V = U/q

The potential difference developed and maintained by source of electrical energy is called electromotive force (emf of ).