2 Marks Questions

Question 12 Marks

What is Lorentz force ?

Answer

Lorentz force is the combination of electric and magnetic force on a point charge due to electromagnetic fields. A particle of charge moving with a velocity $\vec{v}$ in an electric field $\vec{E}$ and a magnetic field $\vec{B}$ experiences a force of
$\vec{F}=q\vec{E}+q\vec{v}\times\vec{B}$

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Question 22 Marks

Write Fleming's left hand rule.

Answer

Fleming Left Hand Rule : According to this rule when we stretch the forefinger, central finger and thumb of our left hand in such a way that the thumb is perpendicular to the plane containing the two fingers then if the forefinger points in the direction of the magnetic field and central finger points in the direction of current, then the thumb will point in the direction of magnetic force on the current carrying conductor.

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Question 32 Marks

What is cyclotron ? State its two limitations.

Answer

Principle of Cyclotron : The working of the cyclotron is based on the fact that a positively charged particle can be accelerated to a sufficiently high energy with the help of smaller values of oscillating electric field by making it to cross the same electric field again and again with the use of strong magnetic field.
Two limitations of cyclotron are:
(i) It can't accelerate electrons : Because electrons have a very small mass, they can't be accelerated by a cyclotron.
(ii) It can't accelerate neutral particles : Cyclotrons can't accelerate particles that have no charge, like neutrons, because they don't interact with electric or magnetic fields.

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Question 42 Marks

Is some work performed by a magnetic field on an electric charge moving in the field ?

Answer

No, because the force $\vec{F}$ acting on the moving charged particle due to magnetic field is always perpendicular to velocity $\vec{v}$, i.e. its displacement $\vec{S}$
Hence $W=\vec{F}.\vec{S}\Rightarrow W=F~S~cos~90^{\circ}=0$

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Question 52 Marks

What is the importance of radial magnetic field in a moving coil galvanometer ?

Answer

In radial field the plane of the coil in all position of the coil remains parallel to the direction of magnetic field, i.e. $\theta=90^{\circ}.$ Hence due to it the torque acting on the coil in all positions of the coil remains constant which will be NIAB sin $90^{\circ}$ i.e. NIAB.

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Physics 2 Marks Questions

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