JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Kinematics

A uniform electric field of

10 N/C

is created between two parallel charged plates (as shown in figure). An electron enters the field symmetrically between the plates with a kinetic energy 0.5 eV. The length of each plate is 10 cm. The angle (

θ

) of deviation of the path of electron as it comes out of the field is ______ (in degree).

Answer: 45

Solution

The electron enters along the plates with horizontal kinetic energy

\frac{1}{2} m v_{x}^{2} = 0.5 e

, so

v_{x}^{2} = \frac{e}{m}

. While crossing the length

L

it gains a transverse velocity

v_{y} = \frac{e E}{m} \cdot \frac{L}{v _{x}}

. The deflection obeys

tan θ = \frac{v _{y}}{v _{x}} = \frac{e E L}{m v _{x}^{2}} = \frac{e E L}{e} = E L = 10 \times 0.1 = 1

. The path leaves the field turned through

θ = 4 5^{\circ}

JEE Main · 2023 · 25 Jan 2023 · Shift 1 · Integer answer

Practise more: all JEE Main PYQs on Kinematics →

More JEE Main questions on Kinematics

A projectile is thrown upward at an angle $6 0^{\circ}$ with the horizontal. The speed of the projectile is 20 m/s when its direction of motion is $4 5^{\circ}$ with the horizontal. The initial speed of the projectile is ______ m/s.
JEE Main 2026View solution →
A river of width 200 m is flowing from west to east with a speed of $18 km / h$ . A boat, moving with speed of $36 km / h$ in still water, is made to travel one-round trip (bank to bank of the river). Minimum time taken by the boat for thi …
JEE Main 2026View solution →
An object is projected with kinetic energy K from a point A at an angle $6 0^{\circ}$ with the horizontal. The ratio of the difference in kinetic energies points B and C to that at point A (see figure), in the absence of air friction is :
JEE Main 2026View solution →
A block is sliding down on an inclined plane of slope $θ$ and at an instant $t = 0$ this block is given an upward momentum so that it starts moving up on the inclined surface with velocity $u$ . The distance $(S)$ travelled by the block before its velocity become zero, …
JEE Main 2026View solution →
A paratrooper jumps from an aeroplane and opens a parachute after 2 s of free fall and starts deaccelerating with $3 m / s^{2}$ . At 10 m height from ground, while descending with the help of parachute, the speed of paratrooper is …
JEE Main 2026View solution →
A bead $P$ sliding on a frictionless semi-circular string $(A C B)$ and it is at point $S$ at $t = 0$ and at this instant the horizontal component of its velocity is $v$ . Another bead $Q$ of the same mass as $P$ is ejected from point $A$ at $t = 0$ …
JEE Main 2026View solution →