A force F, acting on an electric charge q, in presence of an electro- .magnetic field, moves the charge parallel to the magnetic field with velocity v. Then F is equal to (where B and B are electric field and magnetic field respectively)

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Q: 18 (NDA-II/2014)
A force F, acting on an electric charge q, in presence of an electro- .magnetic field, moves the charge parallel to the magnetic field with velocity v. Then F is equal to (where B and B are electric field and magnetic field respectively)

question_subject: 

Science

question_exam: 

NDA-II

stats: 

0,4,11,4,7,2,2

keywords: 

{'magnetic field': [0, 0, 0, 6], 'electric field': [0, 0, 0, 1], 'field': [1, 1, 4, 8], 'qfixbj': [0, 0, 0, 1], 'charge parallel': [0, 0, 0, 1], 'velocity': [0, 2, 2, 6], 'qb': [0, 0, 0, 1]}

The correct answer is option 1: qE.

When a force F acts on an electric charge q in the presence of an electromagnetic field, the force can be expressed as the product of the charge and the electric field.

Option 1: qE

The force F is equal to qE, where E represents the electric field. This option correctly identifies the force as being directly proportional to the charge and the electric field.

Option 2: qfixBj

This option is incorrect because it includes the term "fixBj", which is not commonly used in the context of electromagnetic fields. It also does not take into account the electric field component.

Option 3: q[v x E)

This option is incorrect because it includes the term "[v x E]", which suggests a cross product between the velocity v and the electric field E. The correct formula for the force on a charged particle in an electromagnetic field does not involve the cross product of the velocity and electric field.

Option 4: qB

This option is incorrect because it only includes the term "qB", which represents the product of the charge and the magnetic field. It does not consider the electric field component.

In summary, option 1 (qE) is the correct answer because it