The understandable notes - ELECTRICITY ,Class 10 Part 4

RESISTANCE OF A SYSTEM OF RESISTORS

When more than one resistor is palced in a circuit than the resistance of system is determined  by various formulas and techniques.  Mainly there are two methods of arranging resistors, forst in series and second in parallel. Lets study them deeply.

RESISTORS IN SERIES

When resistors are connected end to end then then they are called to be connected in series. 

Like in the circuit the resistors are connected.end to end. If current is flown through battery then each resistor gets same current because there is only one path from which it can flow. Means if we assume that (I) current is flowing through R1 then same current flow through R2 and same current will flow through R3 as shown in the below diagram.

In the diagram the current flowing through each resistor is same so there is no need to divide and find it.

( Yaar dekho koi chiz series me.connect kaise hoti hai ye to batane ki jarorat nhi hai. Ab jab koi chij series ma connected hoti hai tab current same flow krta hai. Dekho yaar current flow of electrons ya charges hai. Ab charges tabhi divert honge jab ek se jyada path ho pr series mai to aisa hota hi nhi . Agar sare resistors series mai connected hai to current same flow krega. Ye series ke aspect me mcq mai bhi aa sakta hai hi series mai kya chiz same rehte hai. Ab dekhte hao ki potential difference ka kya chakkar hai.)

Potential difference in each resistor which is connected in series are different because potential gets divided between the resistors. So the net potential which is of the cell or battery is the sum of all potential differences in each resistor.Consider the following diagram.

In the diagram if v is the potential differnce of battery and v1  v2 and v3 are the potential differnces across resistors then the sum of v1, v2 and v3 is v means the sum of potential difference of all resistors is total potential of battery.

So the total resistance of a system where all resistors are placed in series are the sum of all resistance of each resistors

(Ab dekho jo current hai vo to same rahega lekin jo potential hai vo change hoga series me kyoki yaar dekho potential basically ek differece hai jiski vajah se current flow hota hai, ab agar beech mai aap resistor laga doge to difference me hindranceto aayegi hi na. Ye yaad rakhna ki agar beech me koi electrical component na ho to potential same rehta hai . To haan chalo maan liya ki potential divide ho gaya. To ab jo potential har resistor ke across hoga unka sabka total sum net potential ke equal hoga jo ki vo potential hoga jo battery exert kregi. Ab dekho is se ye equation nikali hai ki potential ka sum net potential ke equal hoga fir Ohm's lawke sath jugaad baji krke net resistance nikal di. Jugad baji isi liye ki jab bhi kuch prove krna hota hai physics mai tab assumption bahut lagate hai. Haan to series mai bahut chota sa kaam hai sabke potential ko add kr dena bus aur kuch ni. Numericals bhi practice kr lena kyoki unhe yaha likhna is tarah bahut complex hai. Baki agar chahiye to comment kr dena. Mera main motive hai ki tumhe chapter samajhme kai liye 2-2 ghante ki video na dekhni pade jisme se 1.5 ghanta teacher apni kahani sunata hai. )

RESISTORS IN PARALLEL

Resistors are said to be connected in parallel when they are connected in such a way that both of their terminals are connected to the same two points in a circuit. In other words, each resistor shares the same voltage across it, but the current splits between them. 

In the diagram all resistors are connected to same end of wire, so the current splits as it gets more than one path to flow but potential remains same.

( Dekho jo series combination mai hua tha vo yaha nhi hoga. Series mai current same tha to yaha current same nhi hoga. Series mai voltage divide ho rhi thi to yaha voltage ya fir potential difference same rahega kyoki end points same hai.  Aur haan diagram mai ye bhi dikh raha hoga ki voltmeter parallel mai connected hai jabki ammeter series mai connected hai precisionaur accuracy kai liye. To bas yaha se jugaad baji lagake net resistance nikalni hai hai . Aur tumhe bas itna pata.ki voltage same hai aur current divide hua hai.)

So we know that potential across each resistor is same when resistors are connected in parallel but current divides beacuse it gets many path to flow, so the net current is the sum of all current flowing through each resistor.

(Haan to dekho parallel mai potential to same tha difference tha to bas current ka. Ab total current ke formulae se hmne Ohm's law apply kra aur uske baad hmare paas net resistance ka formula aa gaya. Parallel wale questions mai thodi dikkat aati hai kyonki inme reciprocals krne padte hai. Par practice makes a student perfect. Baki ek do numerical krwa deta hu kahi tum kaho ki bas theory krwa rha hai ye to. )

Three resistors with resistances of 12Ω, 18Ω, and 24Ω are connected in parallel. Find the total (or equivalent) resistance of the parallel combination.
( haan to pehle khud krne ki koshish kro agar notebook le kar baithe ho nhi bethe to solve krne ka method dekh lo.)

Solution- If all the resistors are connected in parallel then,

(Yaar dekho ye to numerical hai isme kuch samjhane wala to hai nhi kyonki direct formulae lagna tha. Baki circuit dwale question bhi aayenge jinme circuit dikhakar puchenge ki equivalent resistance batao. Mera laptop tut gaya ek baar naya le lo fir numericals bhi krwa dunga. Baki next part mai teen topics hai chotr chote se aur fir ye chapter finish kyonki exercise wale part mai abhi upload nhi karunga aur bhi kai chapter bache hue hai 10th ke )