__Solved Problems__
Q 1) Calculate the equivalent resistance across AB. Find the
current draw from the battery. You may refer figure 5.1.

a)
Then find the voltage across 9 Ohms resistance.

b)
Find the voltage between AD.

c)
Find the current through 18 Ohms resistance.

Answer :

Resistance across AC = (6/2) = 3 Ohms-----------( as the
resistance are equal, R = r/n )

Resistance across AD = (3+6) // 18 = {9*18/ (9+18)} = 6 Ohms

Resistance across AB = 6+9 =

__15 Ohms__
Now we can find the current drag from the battery by using
this equivalent resistance across AB.

Ohm’s law to

**R**_{ab},
V = IR

60V = I X 15

__I = 4A__**a)**As there are no parallel paths between AB , current through 9 Ohms resistance is equal to

**4A . Ohm’s law to 9 Ohms resistor,**

V = IR

Vdb = 4A x 9 Ohms

__Vdb = 36V__

**b)**Since,

V ab = V ad + V db

V ad = Vab – V db

V ad = 60 – 36

__V ad = 24 V__**c)**Current through 18 Ohms can be calculate by Ohm’s law

Vad = I x 18

I = (24/18) A

__I = (4/3) A__
Q2) Find the
equivalent resistance across AB in every circuit.

i)
Each resistance is 3 Ohms

**Figure 5.2**

Answer :

**Figure 5.2.1**

Figure 5.2.1 shows the way to calculate the equivalent
resistant

__Rab = 3 + 1.5 + 1 + 3 = 8.5 Ohms__**ii)**

Answer :

Then we can simplify this circuit as shown in figure 5.3.2

After therse steps the problem becomes a very simple one.

__Rab = 0.5 Ohms__

**Exercise**

**Q3)**

**i)**Find the current draw from the circuit in figure 5.2 (Q2. i ) if 60 V voltage is given to AB .

**ii)**Find the voltage difference between every resistance

**iii)**Then find the current through every resistance

**Q4)**

**i)**Find the current draw from the circuit in figure 5.3 (Q2. ii ) if 60 V voltage is given to AB .

**ii)**Find the voltage difference between every resistance

**iii)**Then find the current through every resistance

**Q5) i)**Find the total current draw from the battery in Figure 6.1 Ans (3A)

ii) Calculate the power supplied by battery in figure 6.2 Ans(72W)

iii) Find the total resistance seen by the battery in figure 6.3 . find the current draw from it.

Ans (1.5 Ohms , 8A )

**NOTE : In figure 6.1**The resistance are parallel connected (12 Ohms & 6 Ohms ) .

**In figure 6.2**Again you may see that all three resistors are parallel connected.

**In figure 6.3**Again you may see that all four resistors are parallel connected.

to understand these things you need to solve more problems and gain experience.

**B.sc (Engineering undergraduate)**

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