Why do we use half deflection method to determine resistance of a galvanometer?

Why do we use half deflection method to determine resistance of a galvanometer?

The half deflection method is used to find out the resistance of a galvanometer. So the value of G is usually in ohms. So if the value of R is also small then deflection could be large. Hence to bring deflections within scale a high resistance is used in series with a battery.

Why only half deflection method is preferred?

The method that comes to our mind first is by Ohm’s Law. But this method gives some inaccuracy because ideal ammeter must posses zero resistance and voltmeter with infinite resistance. But no devices are idea. Hence we prefer to use half deflection method to measure the unknown resistance value..

What is the concept of half deflection method for finding resistance of coil of the galvanometer?

The half deflection method is the method by which an internal resistance of a cell can help in evaluating value which is considered as high. The deflection of half is considered as a value obtained along with the cell alone.

What is used to find the deflection in galvanometer?

Galvanometer is a sensitive device used to detect very low current. Its working is based on the principle that a coil placed in a uniform magnetic field experiences a torque when an electric current is set up in it. The deflection of the coil is determined by a pointer attached to it, moving on the scale.

How would you determine the resistance of a galvanometer by half deflection method and to find its figure of merit?

Adjust the value of R1 so that deflection is maximum , even in number and within the scale . Note the deflection . Let it be Q. Insert the key k2 also and without changing the value of R2 ,adjust the value of S , such that deflection in the galvanometer reduces to exactly half the value of resistance S.

Why is the bridge method a better way for resistance measurement than Ohm’s law?

Metre bridge works on principle of wheat stone bridge. The Wheatstone bridgemethod is more accurate thanthe other methods ofmeasuring resistances because it uses null method. Hence the internal resistanceof the cell and resistance of galvanometer do not affect the null point.

What are the apparatus needed to determine the resistance of a galvanometer by half deflection method and to find its figure of merit?

A weston type galvanometer, a voltmeter, a battery or battery eliminator, two (10,000 Ω and 200 Ω) resistance boxes, two one-way keys, a rheostat, a screw gauge, a metre scale, an ammeter of given range, connecting wires and a piece of sand paper.

What is resistance of the galvanometer?

the galvanometer resistance equals that value of the variable resistance in the two methods. which gives the same second deflection. A new method which resembles the Kelvin method of. obtaining the resistance of a galvanometer is reported.

How the half deflection method works?

A method of finding the internal resistance of a cell when the value is known to be high. A second cell, a galvanometer and a resistance are connected in series with the cell under test, and the value of the resistance required to give a galvanometer. deflection of half the value obtained with the cell alone is found.

Why does galvanometer show half value?

The quantity of current required to produce a deflection of one division in the galvanometer is called figure of merit of a galvanometer . Its unit is ampere per division . Why is this method called half deflection method? It is so because the deflection is made half by using a shunt resistance S.

Why the resistance of galvanometer is kept small?

Such low resistance galvanometer ( ammeter) is used in series with the circuit to measure the strength of current through the circuit. A low resistance may not introduce any change in the value of current to be measured.

How to determine the resistance of a galvanometer?

Determine the resistance of a galvanometer by half deflection method and to find its figure of merit. To determine the resistance of a galvanometer by half deflection method and to find its figure of merit. A galvanometer is a device used to detect feeble electric currents in a circuit.

How do you reduce deflection in a galvanometer?

Let it be θ. Insert the key also and without changing the value of R, adjust the value of S, such that deflection in the galvanometer reduces to exactly half the value obtained in step 5 i.e., θ/2. Note the value of resistance S.

What happens when current passes through a galvanometer?

As current passes through the coil, it deflects. It can be detected from the deflection on galvanometer needle. The deflection is proportional to the current passed through it. Here, current will flows through th circuit when key k1 is closed and k2 is open. The current flowing through the galvanometer is proportional to the deflection in it.

How do you calculate the figure of Merit in galvanometer?

The figure of merit, K =E / [ (R+G)Q] (2) Where E is the end of the cell and Q is the deflection produced with resistance R. The maximum current that can pass through the galvanometer, I g =nk Where n is the total number of dimension on the galvanometer scale on either side of zero.