
A moving coil galvanometer has N number of turns in a coil of effective it carries a current I. The magnetic field B is radial. The torque acting on the coil is
(A) $N{A^2}{B^2}I$
(B) $NAB{I^2}$
(C) ${N^2}ABI$
(D) $NABI$
Answer
163.2k+ views
Hint: First start with what is torque in general and how it works then try to substitute the general condition with the case of moving coil galvanometer. Use all the information provided in the question in the specific condition of the moving coil galvanometer and get the required answer.
Complete answer:
Let start with what is torque in general.
Torque, $\tau = force \times perpendicular\,dis\tan ce\,between\,the\,forces$
$\tau = F \times b$
Where,
F is force
And b is perpendicular distance between the forces
Torque acting in case of the moving coil galvanometer will be:
$\tau = BIl \times b$
Where, $l \times b$is the area of the moving coil galvanometer(let area be A).
Now from the question, we know;
Number of turns in the moving coil galvanometer is N. Current carrying in the coil is I.
Therefore, substituting all the values we get;
$\tau = NIAB\sin \theta $
where angle formed by direction of magnetic field with normal on the plane of coil be $\theta $.
$\theta = {90^0}$(radial magnetic field given in question)
So, $\sin \theta = \sin {90^0} = 1$
Final torque will be:
$\tau = NIAB$
Hence the correct answer is Option(D).
Note: Here we have find the torque in case of galvanometer and the angle between the direction of magnetic field and the normal drawn on the plane of coil was given ${90^0}$ due to radial magnetic field given in the question. If it is not radial magnetic field then the angle will get changed and hence the required answer.
Complete answer:
Let start with what is torque in general.
Torque, $\tau = force \times perpendicular\,dis\tan ce\,between\,the\,forces$
$\tau = F \times b$
Where,
F is force
And b is perpendicular distance between the forces
Torque acting in case of the moving coil galvanometer will be:
$\tau = BIl \times b$
Where, $l \times b$is the area of the moving coil galvanometer(let area be A).
Now from the question, we know;
Number of turns in the moving coil galvanometer is N. Current carrying in the coil is I.
Therefore, substituting all the values we get;
$\tau = NIAB\sin \theta $
where angle formed by direction of magnetic field with normal on the plane of coil be $\theta $.
$\theta = {90^0}$(radial magnetic field given in question)
So, $\sin \theta = \sin {90^0} = 1$
Final torque will be:
$\tau = NIAB$
Hence the correct answer is Option(D).
Note: Here we have find the torque in case of galvanometer and the angle between the direction of magnetic field and the normal drawn on the plane of coil was given ${90^0}$ due to radial magnetic field given in the question. If it is not radial magnetic field then the angle will get changed and hence the required answer.
Recently Updated Pages
JEE Main 2021 July 25 Shift 1 Question Paper with Answer Key

JEE Main 2021 July 22 Shift 2 Question Paper with Answer Key

JEE Atomic Structure and Chemical Bonding important Concepts and Tips

JEE Amino Acids and Peptides Important Concepts and Tips for Exam Preparation

JEE Electricity and Magnetism Important Concepts and Tips for Exam Preparation

Chemical Properties of Hydrogen - Important Concepts for JEE Exam Preparation

Trending doubts
JEE Main 2025 Session 2: Application Form (Out), Exam Dates (Released), Eligibility, & More

JEE Main 2025: Derivation of Equation of Trajectory in Physics

Displacement-Time Graph and Velocity-Time Graph for JEE

Electric field due to uniformly charged sphere class 12 physics JEE_Main

Degree of Dissociation and Its Formula With Solved Example for JEE

Electric Field Due to Uniformly Charged Ring for JEE Main 2025 - Formula and Derivation

Other Pages
JEE Advanced Marks vs Ranks 2025: Understanding Category-wise Qualifying Marks and Previous Year Cut-offs

JEE Advanced Weightage 2025 Chapter-Wise for Physics, Maths and Chemistry

Charging and Discharging of Capacitor

Wheatstone Bridge for JEE Main Physics 2025

Instantaneous Velocity - Formula based Examples for JEE

Formula for number of images formed by two plane mirrors class 12 physics JEE_Main
