Old is Gold-Magnetic effect of current short answers questions

1.
How can the sensitivity of moving coil galvanometer  be increased?
ans:
a.By increasing the magnetic field of flux density B
b.Increasing the area of coil.
c.By increasing the no. of turns of coil N
d.By reducing the value of torisonal constant K.

2.
A charge particle carrying charge q moves in an electric field E. IF its specific charge is S write an expression of it's acceleration in terms of above entities.
ans:


3.
Magnetic field at the center of the solenoid is double than at its  ends.
ans:


and



4.
Hall voltages are much larger for semiconductors than for good conductors for comparable current,fields  and dimensions why?
ans:
Since the value of n in semiconductors are considerably smaller than in the good conductor since the value of Hall voltage are larger in  semiconductor than in good conductor. As n is inversely proportional to Hall voltage.
( You can answer this question using the logic of current density J as well.)

5.
Can charge particles move through a magnetic field without experiencing any Force explain.
ans:
Yes a charged particles can move through a magnetic field without experiencing any Force, when it moves along the direction of magnetic field that is ϑ =0deg
so,
F=BQVsinϑ F=BQVsin0
F=0N
since it doesn't experince any force in this case

6.
Does a Charged particle moving  through  a magnet field  always experience a force explain.
ans:
No if a charged particles can move through the direction of magnetic field force experiencing by it is 0 that is ϑ =0deg
so,
F=BQVsinϑ F=BQVsin0
F=0N
since it doesn't experince any force in this case.

9.
A current was sent through a helical coil spring. The spring contracted as if it had been compressed. Why?
ans:
Since each loop of a spring will have currents in the same direction, each loop will attract the adjacent loops and therefore the spring will be compressed.

10.
If a magnetic field doesn't work on charged particles how can it have any effect on particle motion
ans: 

dW=q(v⃗ ×B⃗ )⋅v⃗ dtwork is the dot product of force with distance, while the force a magnetic field applies to a moving charge is a cross-product -- that is, since the force is always orthogonal to the distance, no work is done.

Alternatively, if there were magnetic charges, electric fields would be unable to do any work on moving magnetic charges, although they would apply a force.
11.
Can charge particles move through a magnetic field without experiencing any Force explain.

ans:
same as no. 5

12.Two straight current carrying rods are replaced parallel to each other how can one ampere be defined from this arrangement?
ans:
when two straight current carrying rods are replaced parallel to each other how can one ampere be defined as


Hence an ampere is defined as when the current between two parallel conductor is 1A is separated by 1m then they experience a force 2 x 10-7N.per unit length on eachother.

13.
What will be the effect if the magnetic field in a moving coil galvanometer is not radial?
ans:
Ff the magnetic field in a moving coil galvanometer is not radial then the plane of coil is not parallel to the magnetic field and the torque=BINA cosɵ is not same in all cases. So, because of this reason the current sensitivity, voltage sensitivity of galvanometer decrees so it is necessary that the field in moving coil galvanometer is radial.

14.
An electron beam and proton beam are moving parallel to each other in the beginning. Do they always maintain this status? Justify.
ans:
No, they do not always maintain in parallel to each other because electron beam are the negative charge carrier and proton beam are positive charge carries. Moving electrons and protons beam in electric they experience both the electric and the magnetic attraction at normal condition the repulsive force is much strong then the magnetic attraction so the beam diverges while at high velocity the magnetic force become more effective then the beam starts to converging. If electrostatic attraction and magnetic repulsive will be equal, then they move parallel to each other again.

15.
State Ampere's circuital theorem.
ans:

The line integral of the magnetic field B around any closed path is equal to μ₀ times the net current across the area bounded by the path.
ie


16.
A current was sent through a helical coil spring. The spring contracted as if it had been compressed. Why?
same as 9

17,18,19
ans:
same as 9

20.
Explain how the direction of Lorentz force is determined?
ans:
Lorentz force is given by:

F = qvB*sinθ

where:

• F is the force in Newtons
• q is the electric charge in Coulombs
• v is the velocity of a positive (+) charge in meters/second
• B is the strength of the magnetic field in Teslas
• sinθ is the sine of the angle between v and B 

the direction is given by right hand rule: to find the direction of the magnetic force on a positive moving charge, the thumb of the right hand point in the direction of v, the fingers in the direction of B, and the force (F) is directed perpendicular to the right hand palm.


21.
How is magnetic field made radial in moving coil galvanometer?
ans:
The magnetic field can me made radial my placing the soft iron core in the poles of the magnet. In such a way that the angle between normal to the plane of coil and direction of magnetic field is 90deg hence the cylindrical poles make the magnetic field radial.

22.
Why is the cylindrical core of soft iron used in the moving coil galvanometer?
ans:

 The cylindrical soft iron core is used in moving coil galvanometer because of the following reason.

It helps to make field radical such that sinθ =1

It helps to make galvanometer dead beat and

It helps to increase the sensitivity of the galvanometer.

  23.

Define 1 amp in terms of force between current carrying conductors.

ans;

same as 12

24.

A proton moving in a straight line enters a strong mag field along the field direction how will it's path and velocity changes?

ans:

The path and velocity will not change, due to the parallel nature of movement, force is calculated using the formula: 
F=BILsinθ=0
where 
F=force 
B=magnetic field strength 
I=current (if applicable in context) 
L=length of wire 
sinθ= angle of movement 
 so lorentz force is also 0
hence the path and velocity will not change.

25.
Does a charged particle moving through a magnetic field experince a force?
Explain the condition for maximum and mininmum force.
ans:
Yes the charged particle experiences a force called lorentz force
which is given by:


26.
Under what condition does a charge affects a magnet?
ans:
When a charge q moves inside a magnetic field with a velocity v the in this condition it produces magnetic field B then the charge affects  a magnet.
Note this a moving charge inside a uniform magnetic field also produces a force called lorentz force.

27.
State Ampere's circiutal law.
ans:
same as 15

28.
Why does KE of charged particle moving in a magnetic field remains constant?
ans:

Since K.E = ½ mV 2 the force acting on the charge particle while moving in the magnetic field whichis always perpendicular to the velocity vectorchanges only the direction of velocity not the magnitude. So the velocity of the moving particle remains constant.

 29.

What do you mean by magnetic Lorentz force?

ans:

the Lorentz force is the combination of electric and magnetic force on a point charge due to electromagnetic fields. If a particle of charge q moves with velocity v in the presence of an electric field E and a magnetic field B, then it will experience a force,

F=q[E+(v∗B)]$\mathrm{F}=\mathrm{q}\left[\mathrm{E}+\left(\mathrm{v}\ast \mathrm{B}\right)\right]$

 30.

Explain voltage sensitivity of  a moving coil galvanometer.

ans:

Voltage sensitivity of the galvanometer is defined as the deflection produced in the per unit voltage applied to it.

ans:

Voltage sensitivity of the galvanometer is defined as the deflection produced in the per unit voltage applied to it.

It is given by 

  voltagesensitivity=αv=BNAKRwhereα=BINAK

31.

Explain current sensitivity of a moving coil galvanometer.

ans:

Current sensitivity of the galvanometer is defined as the deflection produced in the per unit current flowing through it.

It is given by:




currentsensitivity=αI=BINAKI=BINAKwhereα=BINAK

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