List of top Physics Questions on Moving charges and magnetism asked in UP Board XII

A narrow electron beam passes undeviated through an electric field of \( 4\times10^{4}\ \text{V/m} \) and a magnetic field \( 2\times10^{-3}\ \text{weber/m}^2 \) applied at the same place. The speed of the electron beam will be:
How can a galvanometer be converted into a voltmeter? Explain with the help of a circuit diagram.
Following charged particles are projected perpendicular to a uniform magnetic field with same velocity. Which one will experience maximum force?
Explain Ampere's circuital law. Obtain the expression for the magnetic field inside a current carrying solenoid with its help.
How a galvanometer is converted into an ammeter? The resistance of the coil of a galvanometer is 15 Ω and it gives full scale deflection by a current of 4 mA. How it can be converted into an ammeter in order to measure a current upto 6 A?
A coil of one loop is formed by a wire of length \( L \), and thereafter a coil of 3 loops is formed by the same wire. If the current remains the same in both cases, then the ratio of the magnetic fields at the centre will be:

Option 1: With the help of the given figure, prove that the magnetic field produced at point P is \(B=\dfrac{\mu_0 i}{2d}\left[1+\dfrac{2}{\pi}\right]\). (The wire is hairpin-shaped: a semicircular arc joined to two long straight parallel segments carrying current \(i\); P is at the centre of the arc and the straight segments are a distance \(d\) apart.)
OR
Option 2: What is a radial magnetic field? Explain the working of a moving coil galvanometer with a suitable diagram. How can a galvanometer be converted into an ammeter and a voltmeter?
A circular coil of radius 2.0 cm carries a current of 1.0 A. If the coil has 100 turns, find the intensity of magnetic field at the centre of the coil.
Find out the magnetic moment of a rectangular coil of size 20 cm × 10 cm having 10 A current.
Explain Biot-Savart law. Deduce the formula for magnetic field produced due to a straight current carrying conductor.
OR
An α-particle, accelerated with the potential difference of V volt strikes with a nucleus (atomic number = Z). If r be the nearest distance of closest approach to the nucleus then prove that r = 14·4 Z/V Å.
Obtain the formula for the magnetic field inside a current carrying solenoid with the help of Ampere's circuital law.
OR
Obtain the formula for moment of couple acting on a magnetic dipole in a magnetic field. Define magnetic dipole moment with the help of this.
Explain the motion of a charged particle in a uniform magnetic field. Prove that the radius of the path of a charged particle moving perpendicular to a uniform magnetic field is proportional to the momentum of the particle.
Deduce the formula of force acting between two parallel current carrying conductors.
An electron of energy 10 eV is revolving round a circular path in a uniform magnetic field of \( 10^{-5} \) tesla. Determine the radius of the circular path.
(Given: mass of electron \( m = 9.1\times10^{-31} \) kg, charge \( e = 1.6\times10^{-19} \) C)
Derive the formula for magnetic field due to an infinitely long current carrying conducting wire using Biot-Savart law.
OR
Differentiate between self-induction and mutual induction. The current in primary coil becomes zero in \(10^{-3}\) s and an induced e.m.f. of 1500 volts is produced in secondary. Mutual inductance of coils is 0.5 H. Find the value of initial current in the primary.
Explain Biot-Savart law and find the unit of \( \mu_0 \) with the help of the Biot-Savart equation.
In the figure, currents are flowing in opposite directions in two parallel conductors. What should be the current \( I \) in the conductor X, so that the resultant magnetic field at the point P is zero? Current in the conductor Y is 10 ampere.
Define 1 ampere on the basis of the force acting between two parallel current-carrying conductors.
A proton and an \( \alpha \)-particle enter perpendicularly in a uniform magnetic field with the same velocity. Find out the ratio of their period of revolutions.
State Biot-Savart law. Find the expression for the magnetic field due to a current carrying circular loop at its centre. Also, write down the formula for the magnetic moment of this current loop.
The radius of the circular path of a charged particle in a uniform magnetic field is directly proportional to the:
On the basis of Ampere's circuital law, find the expression for the magnetic field produced by an infinitely long straight current-carrying conductor.
State Gauss’ theorem. Obtain the expression for the intensity of the electric field at a point due to a thin charged wire of infinite length with its help.
Define magnetic moment and write its unit. An electron is moving with the velocity \( 0 \times 10^7 \, \text{ms}^{-1} \) in a circular orbit of radius 0.3 \AA. Calculate its magnetic moment.
The work function of a photoelectric material is 4.0 eV. Find the wavelength of light for which the stopping potential is 5 volt.