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# A small query on Definition of Resistance

Date: 16 Sep 2012   Group: Education    Category: Professional Courses

A resistor is an electrical element which resists the flow of current.

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Author: Smriti    17 Sep 2012      Member Level: Bronze     Points : 6  (Rs 4)    Voting Score: 0

Hello,
Looking at a resistor in a different manner might solve your problem.

A resistor resists flow of current, but when a potential difference (voltage) is applied on the two ends of a resistor, current flows in it. This current is directly proportional to the voltage applied (Ohm's Law).

Now if the resistors are connected in series, there is only one path for current to travel. Current flows from one resistor to the other seamlessly without escaping. This is the reason why the same current flows in resistors connected in series.

To satisfy the Ohm's law, the voltage across each resistor is in proportion to its resistance. The total voltage in the circuit is the sum of individual voltages in each resistor across the circuit and similarly, the total resistance is the sum of individual resistances of the resistors.

So if you see, the sum of voltages in each resistor is equal to the total voltage across the two ends of the circuit, explaining that the current flowing in the circuit (n resistors connected in parallel) is constant.

Author: Gopal Ballav Mishra    17 Sep 2012      Member Level: Silver     Points : 5  (Rs 3)    Voting Score: 0

Basic Ohm's law states that current is directly proportional to voltage applied or the potential difference.

V = I * R or I = V / R

As, resistance increases, current decreases, but in series connection the current is constant (just assume) , and the resistance increases, but to compensate the increase in resistance the potential difference also increases, so it nullifies the effect of the rise in resistance and the ratio remains constant.

Example -

Between a point A and B , we have 1 resistor of 2 ohms and the current supplied is 2 Amperes, so the potential difference from Ohm's law comes out to be 4 Volts.
Now, if we add another 2 ohms resistor in series, the resistance increases to 4 ohms, but current remains constant as the potential difference also increases to compensate the effect of increasing the resistance, so we have 2 different voltages in both the resistors, and when we see the voltage difference between A and B, it is 8 volts.

So, you see V / R = 4 / 2 = 8 / 4 = I

Author: JyotiS    17 Sep 2012      Member Level: Diamond     Points : 5  (Rs 3)    Voting Score: 0

In practical circuits, there is always some loss of power when ever current flows through a wire. This power dissipation is in the form of heat developed due to the hindrance experienced by the charge carriers in the wire. This hindrance or opposition to the flow of charge carriers is what is known as RESISTANCE.
Now when we say that Current remains the same for a number of resistors connected in series, we are not telling that exactly same physical hindrance is felt by the charge carriers, But here we are saying that the change in Voltage is adjusted such that the total effect remains the same. In series, charge carriers or the current does not have any alternate path for travelling, so the same charge carriers flows through all the resistors.
This total effect can be very well understood by looking at the Ohm's Law:
V = I * R
This means that the change in voltage and total effective resistance across the N number of resistors are adjusted such that the net current flowing through the wire connected in series remains the constant.

Author: Jatin    22 Sep 2012      Member Level: Silver     Points : 3  (Rs 2)    Voting Score: 0

According to the ohm's law V=IR

where V=voltage across the resistor

I=current

R=resistance

In case of a parallel combination of resistors the voltage remains constant but the current varies because it gets divided across the different branches according to the resistance value of that branch

Whereas in case of series combination, the current remains constant because it has to pass through the same path but the potential difference across each resistor keeps on varying according to their value.

Author: NITIN YADAV    23 Sep 2012      Member Level: Gold     Points : 2  (Rs 2)    Voting Score: 0

Resistance is the hindrance to flow of current through a element. Its SI unit is ohm.The resistance of an object is defined as the ratio of voltage across it to current through it. R=V/I.
According to ohms law the graph of voltage and current is proportional. On the basis of this devices are divided as ohmic and non-ohmic. Resistors follows ohms rule while there are some devices do not follow ohm's rule. These devices are zener diode , diode, Transistor etc.

Author: rahul    25 Sep 2012      Member Level: Bronze     Points : 2  (Rs 1)    Voting Score: 0

There is a simple answer my dear friend. You may take the voltage source as a person who already knows the amount of resistance that has been connected in the circuit.
So certainly a lesser amount of current flows when an extra resistance is added in the circuit.
Take one case when 10A current flows through a resistance. if we connect two same resistances in series in another case, current is going to be halved(5A).

Author: Akshay Swami    25 Sep 2012      Member Level: Bronze     Points : 2  (Rs 1)    Voting Score: 0

Resistance is the Bariar in flow of current.
And resistance can be minimise by decreasing the temperature of a conductor.
Because of that some types of computers are placed in AC rooms.
In ex.- ATM machins, Super computers.

Author: [Anonymous]    29 Nov 2012      Member Level: Silver     Points : 2  (Rs 2)    Voting Score: 0

Resistance may be defined as that property of a substance which opposes the flow of electricity through it.

It is represented by "R".
The unit of resistance is Ohm.

Resistance depends upon the following factors:
(a) The resistance of a conductor varies directly as its length.
(b)The resistance of a conductor varies inversely as its cross-section.
(c)The resistane of conductor depends on the nature of the material.
(d)The resistane of conductor depends on its temperature.

Hence, R=pL/A.

Author: [Anonymous]    28 Dec 2012      Member Level: Silver     Points : 5  (Rs 4)    Voting Score: 0

Resistor is an electrical element which resists the flow of current. When n resistors are connected is series, the resistance to flow of current by each resistor will add up and total resistance is sum of individual resistance by each resistors. Then by Ohm's law, if we are connecting a voltage source across this branch, current flowing will be voltage/(total resistance[sum of n resistance]).

If we are using n+1 resistors instead of n, then total resistance changes and thus total current through the branch also changes. ie total current through the branch will be voltage/(total resistance[sum of n+1 resistance]).

If you are not getting the point just imagine a water tank and a pipe connection to it. If you are interconnecting 3 separate pipes to connect to a tap in which 2 are wide like 10cm diameter and one is 5cm diameter. But the water coming through the pipe will not change even if you use 1 pipe 10cm diameter and 2 pipe 5cm diameter. This is only because the volume of water one 5cm diameter pipe can pass will be the water coming out of it.

I think you got the point.

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