Tag: physics

Questions Related to physics

You are sitting in a room in which a strong magnetic field is directed from your left towards right. A beam of electrons is directed from front towards you. What would be the direction of magnetic force on this beam ?

physics magnetic effect of electric current fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. downwards.

  2. upwards.

  3. towards right 

  4. towards left 

Show answer
Correct Option: A
Explanation:
The direction of the magnetic field is from left to right, the direction of the beam of electrons is from your front hence the direction of the current is from back to front. Now by applying Fleming left hand rule we can find that the direction of the magnetic force on the beam of electron is downwards.

An electron is travelling along the x-direction. It encounters a magnetic field in the ydirection. Its subsequent motion will be

physics magnetic effect of electric current fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. straight line along the x-direction

  2. a circle in the zx-plane

  3. a circle in the yz-plane

  4. a circle in the xy-plane

Show answer
Correct Option: B
Explanation:

The magnetic force acting on a charged particle is given by 

$\vec{F}=q(\vec{v}\times \vec{B})$
Hence direction of force acting one electron is $\hat{i}\times \hat{j}=\hat{k}$
The force experienced is in z-direction. So the particle moves in the zx plane.

An electric current runs counterclockwise in a rectangular loop around the outside edge of the page which lies flat on your table. A uniform magnetic field is then turned on directed parallel to the page from the top to bottom. The magnetic force on the page will cause:

physics magnetic effect of electric current fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. the left edge to lift up

  2. the right edge to lift up

  3. the top edge to lift up

  4. the bottom edge to lift up

Show answer
Correct Option: C
Explanation:

Current is flowing anticlockwise in the rectangular loop and in the upper edge of page current is flowing towards left and magnetic field is from top to bottom , so by applying Fleming's left hand rule the direction of force is found to be in the upward direction, lifting the top edge up.

A positive charge is at rest in a uniform magnetic field directed to the right. What force does the positive charge feel, due to the magnetic field?

physics magnetic effect of electric current fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. An upward force.

  2. A downward force.

  3. A force to the left.

  4. No force is felt.

Show answer
Correct Option: D
Explanation:
For experiencing a magnetic force on a charge  particle, the particle should move in the magnetic field with some velocity. As the velocity of the particle is zero so, the force on the particle is also zero.

The direction of force on a current carrying conductor placed in a magnetic field is given by :

physics magnetic effect of electric current fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. Fleming's Left Hand Rule

  2. Fleming's Right Hand Rule

  3. End Rule

  4. Right Hand Palm Rule

Show answer
Correct Option: A
Explanation:

The direction of this force is always right angles to the plane containing both the conductor and the magnetic field, and is predicted by Fleming’s Left-Hand Rule.

A vertical wire carries a current in upward direction. An electron beam sent horizontally towards the wire will be deflected (gravity free space) :

physics magnetic effect of electric current fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. towards right

  2. towards left

  3. upwards

  4. downwards

Show answer
Correct Option: C
Explanation:

$F= q(\vec{v} \times \vec{B})= (-e)( -v\hat{i}\times (-B\hat{k}))=evB\hat{j}$
Thus, force on the electron beam is along the +ve y-axis.

In _______ Fleming Left hand rule is not used.

physics magnetic fields and electromagnetism fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. Electric fan

  2. Mixer

  3. Computer

  4. Electric generator

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Correct Option: D

Fleming's left hand rule is used to find

physics magnetic fields and electromagnetism fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. Direction of magnetic field 

  2. Direction of current

  3. Direction of magnetic force acting on conductor

  4. None of these

Show answer
Correct Option: A

An electron is moving vertically downwards at any place. The direction of magnetic force acting on it due to horizontal component of earth's magnetic field will be

physics magnetic fields and electromagnetism fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. towards east

  2. towards west

  3. towards north

  4. towards south

Show answer
Correct Option: B
Explanation:

According to Fleming left hand rule, if the direction of horizontal component of earth's magnetic field is from south to north and direction of velocity of electron is downwards then the direction of the force given by the thumb is towards west.

An electron and a proton travel with equal speeds and in the same direction, at $90^o$ to a uniform magnetic field. They experience forces which are initially

physics magnetic fields and electromagnetism fleming's left hand rule magnetic force magnetic force on a moving charge and current carrying wire

  1. in opposite direction and differ by a factor of about 1840

  2. in the same direction and differ by a factor of about 1840

  3. equal in magnitude but in opposite directions

  4. identical

Show answer
Correct Option: C
Explanation:
As both of the particle having same speed and in the same field at same angle, they will be experiencing same force but in opposite direction as they are opposite in charge.