galvanometer

Question 1

diff galvanometer

Answer 1

it is a meter used to detect , measure the intensity and determine the direction of very weak electric currents

Question 2

scientific idea of operation

Answer 2

1. it depends on the magnetic torque acts on a rectangular coil carrying an electric current placed in an external magnetic filled
2. the magnetic Torque depends only the electric current intensity at constant ( B , A , N , SIN seta )

T & I at sonstant other factor

Question 3

what is the construction and uses of each substance

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Answer 3

1. a coil warpped around a soft iron core
2. Jeweled bearing which the coil pivoted between concave poles of U shaped magnet]
3. pair spiral spiring restrain the rotational motion of coil and serve as current lead to the coil
4. pointer fixed on the coil axis rotate with its rotation on middle zero scale

Question 4

what is the operating of galvonmeter

Answer 4

1. when the weak electric current passes through the coil , magnetic forces will produce tourque ( the pointer and the coil will rotate either in clock wise or counter anti clock wise dirction depending on the dirction of the measured current
2. UNTI the mechanical resisting torque of the spring equals the magnetic tourque produced by the current then the pointer stops on the scale to represen a measure of the current magnitude
3. use to meacure current intinstey and dirction

Question 6

diff the sensitivty of galvanometer

and rule and unit

Answer 6

1. it is bthe angle of the scale deflection per unit current intenstity passing through its coil
2. senstivity = seta \ I_g
3. amp/each scale divition , radian / amp , degree / milli amp

Question 7

the sensitivty of galvonometer is controlled according to

Answer 7

1. the spring tourque
2. the firction in the bearings

Question 8

presence of pair spiral springs in the galvanometer GR

Answer 8

1. serve as current leads to the coil
2. makes resisting tourque restrain the rotational motion of coil by which

• the pointer stops on its reading when the resisting torque equels the magnetic torque produced by the current
• the coil returns back to its zero position when the measured current cut when the two tourque are equel

Question 9

presence of the jeweled bearings in the galvnometer GR

Answer 9

to minimize the firction with the axis of the coil during the rotation which sensitivity of a galvonmeter increases

Question 10

the coil is wrapped around a soft iron core in the galvanometer GR

Answer 10

because soft iron has high magnetic permeability so it concentrates the magnetic flux lines which the magnetic flux density increases and also the torque will increases and so the sensitivity of galvnometer increases

Question 11

the permanet magnet used in the galvnometer has concave poles GR

Answer 11

to produce radial magnetic filed which

1. concentrates the magnetic flux lines
2. the magnetic flux lines acts as diameters always normal on the two sides of the coil to produce maximum torque ( coils olane alwys parallel to the magnetic flux lines ) that will keep ( seta ) is constant = 90 during rotation to be sure that the pointer deflection will be directly proportional to the current intensity only the coil

Question 12

the galvanometer has uniform scale

Answer 12

because the magnetic torque is directly proportional to on the elctric xurrent intensity at constant ( B , A , N , SIN seta t & I at constant other factor

Question 13

the galvnometer couldnot be use couldnt be used to measure high current intensities

Answer 13

passing high current causes damage

because the copper will melt affected by the rise in temperature due to its ohmic resistance