A circular coil having $N$ turns and radius $r$ carries a current $I$. It is held in the $XZ$ plane in a magnetic field $B \hat{i}$ . The torque on the coil due to the magnetic field is :
- $B \pi r^2 IN$
- $ \frac{B r^2 I}{\pi N}$
- Zero
- $ \frac{B \pi r^2 I}{N}$
The Correct Option is A
Solution and Explanation
$ = NI(\pi r^2) \hat{j}$
Torque on loop (coil) = $\vec{M} \times \vec{B}$
$ = NI (\pi r^2) B \sin 90^{\circ} ( - \hat{k})$
$ = NI \pi r^2 B ( - \hat{k} ) $
Top Questions on Moving charges and magnetism
- Two long parallel wires X and Y, separated by a distance of 6 cm, carry currents of 5 A and 4 A, respectively, in opposite directions as shown in the figure. Magnitude of the resultant magnetic field at point P at a distance of 4 cm from wire Y is \( 3 \times 10^{-5} \) T. The value of \( x \), which represents the distance of point P from wire X, is\( \_\_\_\_\_\) cm. (Take permeability of free space as \( \mu_0 = 4\pi \times 10^{-7} \) SI units.)
- JEE Main - 2025
- Physics
- Moving charges and magnetism
- The correct decreasing order of spin only magnetic moment values (BM) of $ \text{Cu}^+ $, $ \text{Cu}^{2+} $, $ \text{Cr}^{2+} $ and $ \text{Cr}^{3+} $ ions is:
- JEE Main - 2025
- Chemistry
- Moving charges and magnetism
- Total number of molecules/species from the following which will be paramagnetic is ________________________. \[ O_2, O_2^+, O_2^-, NO, NO_2, CO, K_2[NiCl_4], [Co(NH_3)_6]Cl_3, K_2[Ni(CN)_4] \]
- JEE Main - 2025
- Chemistry
- Moving charges and magnetism
- A galvanometer of resistance 8 $\Omega$ gives full scale deflection for a current of 4 mA. The resistance to be connected in series to the galvanometer to convert it into a voltmeter to measure a maximum potential difference of 20 V is
- TS EAMCET - 2025
- Physics
- Moving charges and magnetism
- If the time period of an alpha particle rotating in a circular path of radius 2 fermi is 3.14 $\mu$s, then the magnetic field induced at the centre of the circle is nearly
- TS EAMCET - 2025
- Physics
- Moving charges and magnetism
Questions Asked in JEE Main exam
The dimension of $ \sqrt{\frac{\mu_0}{\epsilon_0}} $ is equal to that of: (Where $ \mu_0 $ is the vacuum permeability and $ \epsilon_0 $ is the vacuum permittivity)
- JEE Main - 2025
- Electromagnetic waves
Given below are two statements:
Statement (I):
are isomeric compounds.
Statement (II):
are functional group isomers.
In the light of the above statements, choose the correct answer from the options given below:- JEE Main - 2025
- Isomerism
- The formation enthalpies, \( \Delta H_f^\circ \) for \( \text{H}_2 \) and \( \text{O}_2 \) are 220.0 and 250.0 kJ mol\(^{-1}\), respectively, at 298.15 K, and \( \Delta H_f^\circ \) for \( \text{H}_2\text{O} \) (g) is -242.0 kJ mol\(^{-1}\) at the same temperature. The average bond enthalpy of the O-H bond in water at 298.15 K is:
- JEE Main - 2025
- Thermodynamics
- In a group of 3 girls and 4 boys, there are two boys \( B_1 \) and \( B_2 \). The number of ways in which these girls and boys can stand in a queue such that all the girls stand together, all the boys stand together, but \( B_1 \) and \( B_2 \) are not adjacent to each other, is:
- JEE Main - 2025
- Permutations
For the AC circuit shown in the figure, $ R = 100 \, \text{k}\Omega $ and $ C = 100 \, \text{pF} $, and the phase difference between $ V_{\text{in}} $ and $ (V_B - V_A) $ is 90°. The input signal frequency is $ 10^x $ rad/sec, where $ x $ is:
- JEE Main - 2025
- AC Circuits
Concepts Used:
Moving Charges and Magnetism
Moving charges generate an electric field and the rate of flow of charge is known as current. This is the basic concept in Electrostatics. Another important concept related to moving electric charges is the magnetic effect of current. Magnetism is caused by the current.
Magnetism:
- The relationship between a Moving Charge and Magnetism is that Magnetism is produced by the movement of charges.
- And Magnetism is a property that is displayed by Magnets and produced by moving charges, which results in objects being attracted or pushed away.
Magnetic Field:
Region in space around a magnet where the Magnet has its Magnetic effect is called the Magnetic field of the Magnet. Let us suppose that there is a point charge q (moving with a velocity v and, located at r at a given time t) in presence of both the electric field E (r) and the magnetic field B (r). The force on an electric charge q due to both of them can be written as,
F = q [ E (r) + v × B (r)] ≡ EElectric +Fmagnetic
This force was based on the extensive experiments of Ampere and others. It is called the Lorentz force.