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(A) : An electron moving with uniform ve...

(A) : An electron moving with uniform velocity enters uniform magnetic field perpendicularly and then a uniform electric field in the same direction. Nature of paths followed by electron in both the fields will be same.
(R) : The force applied by magnetic and electric field on electron are in the same direction.

A

Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'.

B

Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A'

C

'A' is true and 'R' is false

D

'A' is false and 'R' is false

Text Solution

AI Generated Solution

The correct Answer is:
To solve the question, we need to analyze the two statements (A) and (R) regarding the motion of an electron in a magnetic field and an electric field. ### Step-by-Step Solution: 1. **Understanding the Motion in a Magnetic Field:** - When an electron enters a uniform magnetic field perpendicularly (at a 90-degree angle), it experiences a magnetic force given by the formula: \[ F_B = q \cdot v \cdot B \cdot \sin(\theta) \] where \( q \) is the charge of the electron, \( v \) is its velocity, \( B \) is the magnetic field strength, and \( \theta \) is the angle between the velocity and the magnetic field. Since the angle is 90 degrees, \( \sin(90) = 1 \), thus: \[ F_B = q \cdot v \cdot B \] - This force acts perpendicular to the velocity of the electron, causing it to move in a circular path. 2. **Understanding the Motion in an Electric Field:** - When the same electron enters a uniform electric field, it experiences an electric force given by: \[ F_E = q \cdot E \] where \( E \) is the electric field strength. - The direction of this force is along the direction of the electric field, meaning the electron will accelerate in a straight line in the direction of the electric field. 3. **Comparing the Paths:** - In the magnetic field, the electron follows a circular path due to the perpendicular force acting on it. - In the electric field, the electron follows a straight line path due to the constant force acting in the direction of the electric field. 4. **Evaluating Statement (A):** - Statement (A) claims that the nature of paths followed by the electron in both fields will be the same. This is **false** because the paths are different: circular in the magnetic field and straight in the electric field. 5. **Evaluating Statement (R):** - Statement (R) claims that the forces applied by the magnetic and electric fields on the electron are in the same direction. This is also **false** because the magnetic force acts perpendicular to the motion of the electron, while the electric force acts in the direction of the electric field. ### Conclusion: Both statements (A) and (R) are false.
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