Correct Answer - Option 3 : The proton velocity will increase in magnitude
CONCEPT:
Lorentz force:
-
It is defined as the force exerted on a charged particle q moving with velocity v through an electric field E and magnetic field B. The entire electromagnetic force on the charged particle is called the Lorentz force and is given by
⇒ FL = qE + qvBsinθ
- A charged particle experiences a force when it moves in a magnetic field.
- The magnetic force is given as,
⇒ F = qvBsinθ
Electric field intensity:
- It is defined as the force experienced by a unit positive test charge in the electric field at any point.
- The positive charge experiences a force in the direction of the electric field and the negative charge experiences a force in the direction opposite of the electric field.
\(⇒ E=\frac{F}{q_{o}}\)
Where, F = force due to magnetic field, m = mass, q = magnitude of charge, v = speed of charge, E = electric field, B = magnetic field and θ = angle between v and B
EXPLANATION:
- Since the direction of the magnetic field and the velocity of the proton is the same so,
⇒ θ = 0°
- Magnetic force on the proton is,
⇒ FB = qvB × sin0
⇒ FB = 0 -----(1)
- The force due to electric field on the proton is given as,
⇒ FE = eE -----(2)
- The positive charge experiences a force in the direction of the electric field and the negative charge experiences a force in the direction opposite of the electric field.
Where e = charge on a proton
Therefore total force on the proton is given as,
⇒ FL = eE -----(3)
- The total force on the proton is in the direction of its motion, therefore we can say that the proton will accelerate without changing the direction.
- So the proton velocity will increase in magnitude. Hence, option 3 is correct.