12)Why is post office box so named?
Post office box is named as post Office box because the instrument was designed to
measure the resistance the telegraph wire in a post office.
The orientation of the magnet here with respect to earth's magnetic field is the magnet is perpendicular to the earth's magnetic field.
No, an ammeter is not a low-resistance galvanometer. An ammeter is an instrument used to measure electric current, while a low-resistance galvanometer is a device used to detect small electric currents. The two instruments measure different parameters and thus require different designs. An ammeter typically has a very low resistance, while a low-resistance galvanometer has a much higher resistance.
-Yes, we can use Kirchhoff’s laws to both a.c. and d.c. It is because the
Conservation laws of charge and energy are followed by both a-c. and
d.c. Kirchhoff’s first law concludes the conservation of change and the
second law concludes the conservation of energy.
Kirchhoff's laws are related to the law of conservation ff Charge and the law of conservation of energy. The first Kfrchhoff's law is based on the law of conservation of charge and the second law in based upon
Of conservation Of energy.
The Wheatstone bridge is not suitable for measuring very low resistance because it is based on a ratio of two resistances, and the resolution of the bridge decreases as the ratio approaches 1. This means that the Wheatstone bridge is not accurate enough to measure very small changes in resistance.
A slide wire bridge is called meter bridge because in a slide wire, wire of
one meter is used to form Wheatstone bridge and it works on
Wheatstone bridge principle.
A meter bridge is also called a slide wire bridge because the jokey is
slided over the wire of one meter length in the bridge while doing the
experiment.
Ohm's law can be used to analyze simple electric circuits only but it
cannot be used to analyze the complicated electric circuits containing
many components and loops. It can be done by using Kirchhoff's
So, Kirchhoff's laws are preferred over ohm's law in an electrical
because Kirchhoff's laws can used to analyze the circuits con
manysources of emf.
When the circuit contains more than onesourceof emf and the current is
divided into many branches, the circuit will very complicated . Then
we cannot analyze the circuit by using only ohm's law. But in this case
Kirchhoff's laws simplify it to analyze the circuit.
We should not use Wheatstone bridge for measuring high resistance
because in this case we have to use a galvanometer of high internal
resistance. It will make low current flow through flow through the galvanometer
which will make it less sensitive.
Kirchhoff's first law is based on the principle Of conservation of charge and
is based on the principle of conservation energy.
When the resistances in the four arms of the bridge are of the same order, the bridge is most sensitive.
The reason for this is that the balance point is obtained at the middle portion of the meter bridge wire which will be more accurate.
Copper wire is not used in potentiometer because of its low resistivity. As a result resistance of the wire will be small and it will difficult to get a null point during the experiment.
The longer is the length of the potentiometer wire, the higher is the accuracy because the potential drop on the wire per unit length decreases as the length of the Wire increases .Hence the potentiometer measures emf more accurately.
With increase in length the potentiometer becomes more sensitive. The fall of potential is proportional to the length of the wire only if the wire is of uniform thickness.
The potential difference per unit length of the wire of a potentiometer is called its potential gradient. Smaller the potential gradient, better its sensitivity.
Every joint introduces some resistance which is not taken into consideration. This may introduce error in the measurement. Further it is not necessary that the wire has uniform thickness throughout its length
If the cross sectional area of potentiometer wire is not uniform , then potential gradient will not be same at all places on the potentiometer wire. Consequently, the measured value of potential difference will not be correct.
When we use voltmeter in an electrical circuit it draws current from the circuit so it measures only the potential difference across the circuit but not the emf of cell. But if we use potentiometer, at null point no current is drawn from the cell. Also, the potential measured by the voltmeter is always less than emf.
Kirchhoff’s current and voltage laws depend on conservation of energy. Both of Kirchhoff's laws can be understood as corollaries of the Maxwell equations in the low-frequency limit. They are accurate for DC circuits, and for AC circuits at frequencies where the wavelengths of electromagnetic radiation are very large compared to the circuits.
Non-ohmic resistors are resistors that do not obey Ohm's law, meaning their resistance does not depend linearly on the applied voltage. Examples include thermistors, photoresistors, tunnel diodes, and field-effect transistors. A galvanometer is a device used to measure electric current. It can be converted into an ammeter by connecting a low resistance in series with the galvanometer. This resistance should be low enough that it does not significantly affect the current being measured, but...
If the polarity is reversed in a meter bridge, then the measurements taken by the bridge will be incorrect. This is because the bridge relies on the current running through the circuit in order to measure the resistance of the circuit. If the polarity is reversed, then the current will run in the opposite direction, resulting in incorrect measurements.