Combination of resisrtances

2. Q1. What do you mean by resistance of a
conductor?
Ans The opposition offered to flow of current is
called resistance of a conductor. Also R=V/I
Q2. On what factors resistance depends?
 Length
 Area
 Temperature
 Nature of the material.
Q3. How resistance does depend upon length?
Ans RαL
Q4. How can we join two or more resistances?

3. We can combine resistances in two ways:-
 1. Series Combination.
 2. Parallel Combination.
Series Combination Parallel Combination

4. When two or more resistors are connected end to end consecutively, they are
said to be connected in series combination. The combined resistance of
any number of resistances connected in series is equal to the sum of the
individual resistances.
Here, Veq = V1 + V2 + V3
IR= IR1 + IR2 + IR3
Req = R1 + R2 + R3
Note:-
 The current through the circuit will remain same in series combination.
 The equivalent potential difference is the sum of the individual potential
difference across each resistor.
 As a result, equivalent resistance becomes the sum of individual
resistances.

5.  Two or more resistances are said to be connected in parallel
connected when they are connected between two points and each has a
different current direction. The current is branched out and recombined as
the branches intersect at a common point in such circuits.
Ieq = I1 + I2 + I3
V / Req = V / R1 + V / R2 + V / R3
1 / Req = 1 / R1 + 1 / R2 + 1 / R3
NOTE:-
 The equivalent current through the circuit is the sum of individual
currents through each branch of the circuit.
 The potential difference across the two terminal points of the circuit
remains the same.
 the equivalent resistance is always lesser than all the individual
resistances.

6. SERIES COMBINATION PARALLEL COMBINATION
 If one of the components
fails or shorted, the rest of
the components of the circuit
do not work.
 Every device require
different amount of current,
which is not possible in
series circuit
 All devices have only one
switch, so we cannot operate
individual device separately.
 Devices do not work
properly because of diferent
voltage reaches at them
 If one of the components
fails or shorted, the rest of
the components of the
circuit work usually.
 This is possible in parallel
circuit
 Every device has its own
switch, so we can operate
it seperately
 Every device get same
voltage so it works
properly

7. Q1. What is the equivalent resistance in series
combination?
Q2. What is the effect on current when
resistances are connected in series?
Q3. What is the equivalent resistance in Parallel
combination?
Q4. What is the effect on potential when
resistances are connected in parallel?

8. Q1 Study the following electric circuit and find (i) the
current flowing in the circuit
and (ii) the potential difference
across 10 Ω resistor.
Q2. Find the current drawn from
the battery by the network of four
resistors Shown in the figure.
Q3. Find the current flowing
through the following electric
circuit.