what is the concept of equivalent resistance ?

Question

And why is it that the series connection need to be measured in ammeter and parallel connection need to be measured in voltmeter ? [ am i right ] ? or vice versa


Need answer ASAP

Answer 1

Equivalent resistance means exactly what it sounds like. That is What would be the resistance

measured in Ohms, of ONE RESISTER if it were

put in place of an entire network of resistors.

for example two parallel 6 ohm resistors would

behave towards a voltage sourse exactly as one 3 ohm resistor.



The formula for equivelent resistance for a pair of

parallel resistors is 1/R = 1/Rsub1 + 1/Rsub2

if Rsub1 is first resistor and Rsub2 is second resistor and R is the equivelent resistance of the entire circuit. This formula extends to 3 or more resistors

1/R = 1/Rsub1 + 1/Rsub2 + 1/Rsub3.....+1/Rsub n

if you have n parallel resistors



Now for a circuit of resistors in series, the formula

is easier.

For two resistors in series Total Resistance = First plus 2nd

or R = Rsub1 + Rsub2



I never had a lab where I got to work with this as I'm a math person, not an electronics person. However math gives us tools to know what should happen in the lab.

I would conjecture that you are right, series connections should be measured with ammeter

and parallel connection with volt meter. Here's why.

When unequal resistors are in parallel different

currents flow through the resistors however

VOLTAGE DROP across the parallel resistors

must be a fixed number. So if you can determine

the voltage drop and have a current measurement

from somewhere in series with the circuit,

We know that E = IR by George Simon Ohm's law so equivelent resistance R = E/I where E

is Electromagnetic force measured in volts.



If you have learned to use V to represent emf, substitute V for E in the formula I gave.



Alternatively, if unequal valued resistors are in series, the voltage drops across each are different however a FIXED CURRENT I flows through the series circuit. So if you can determine

the value of that fixed current and determine the voltage drop across the entire group of series resistors, now you can use ohms law to get the

resistance of the entire group of series resistors.



Basically, when solving networked resistance

problems, you want to replace every group of

parallel resistors with one resistor, and every group of series resistors with one resistor until

you reduce your problem to A SIMPLE SERIES

CIRCUIT or a SIMPLE PARALLEL CIRCUIT.

Then use the same technique to replace that

with ONE EQUIVELENT RESISTANCE and

that is a single number (in ohms) that represents

the ENTIRE NETWORK AS IF IT WERE

ONE -----\/\/\/\/\/\/\------ Simple resistor!!!

Answer 2

The equivalent resistance concept is often used while solving DC(and also AC) circuit problems. It is a method by which we try to combine all the resistances in a circuit into one resistance in order to simplify the circuit. Resistances in simple series, are algebraically added to get the equivalent resistance and in simple parallel, the reciprocal of resistances is algebraically added to get the reciprocal of equivalent resistance. Now, an ammeter is a device with a low resistance and we know that it is used to measure the current flowing in the circuit. A low resistance device hardly impedes the current flow in the circuit and thus gives us quite an accurate result. A voltmeter on the other hand is used to measure the potential drop across any two points in the circuit. It is usually added in parallel to the device across which we have to get a voltage reading. A voltmeter is a device with a high resistance and thus impedes the current flowing through it massively and thus draws very small current for itself and gives an almost accurate reading. We can use potentiometers for even more accurate readings than voltmeters. Contact me if you have any doubt or queries.

Answer 3

Equivalent resistance is the resistance that you would read across a network of resistors. Any network of resistors can be simplified to an equivalent resistance.



Current through a resistance is measured by putting an ammeter in series with the resistance.

Voltage across a resistance is measured by putting a voltmeter across (parallel to) the resistance.



If you are having trouble visualising current and voltage, try thinking in terms of water flowing in a pipe. Current = flow rate, voltage = pressure drop.

Answer 4

A wire exhibits a certain resistance per foot of wire. Double the length to two feet and it exhibits twice the resistance. In like manner any two resistors in series can be replaced (in fact or on paper) with a single equivalent resistor equaling their sum. For resistors in parallel, electrons have two possible paths (like water flowing through two parallel pipes) and the combined equivalent resistance must be less than the resistance of a single resistor of the pair. An ammeter exhibits negligible resistance and can be placed in series with series resistors to measure current without affecting current. A voltmeter (usually) has a high resistance and can not be placed in series with series resistors without stopping current. A voltmeter can be placed across resistors in parallel to measure the electrical pressure (voltage) driving current, and knowing the value of each resistor permits the current through each to be calculated (especially within a complex circuit).

Answer 5

When resistances are connected in series - parallel or just parallel you need to combine them to find total circuit resistance or a part of a circuit resistance and this is called an equivalent resistance.

You connect an ammeter in series with the current running in the circuit similar to measuring water flow in a pipe.

Voltage needs to be in parallel to measure voltages or the potential difference in the circuit similar to measuring pressure.

Answer 6

no longer understanding the context in which you desire to apply this expression, i could use = "l. a. loi du moindre attempt." that is no longer a be conscious-to-be conscious translation regardless of the undeniable fact that it ought to paintings, observing the context.