CBSE 2026 · Region 1 · Set 3 · Q23 · 3 marks
Figure shows a narrow beam of electrons entering with a velocity of $\displaystyle 3 \times 10^{7} \mathrm{~m} / \mathrm{s}$, symmetrically through the space between two parallel horizontal plates $\displaystyle \mathrm{P}_{1} \mathrm{P}_{1}^{\prime}$ and $\displaystyle \mathrm{P}_{2} \mathrm{P}_{2}^{\prime}$ kept $\displaystyle 2$ cm apart.
If each plate is $\displaystyle 3$ cm long, calculate the potential difference V applied between the plates so that the beam just strikes the end $\displaystyle \mathrm{P}_{2}^{\prime}$.
If each plate is $\displaystyle 3$ cm long, calculate the potential difference V applied between the plates so that the beam just strikes the end $\displaystyle \mathrm{P}_{2}^{\prime}$.Marking-scheme solution
Since $\displaystyle \mathrm{a}=\dfrac{\mathrm{qE}}{\mathrm{m}}=\dfrac{\mathrm{qV}}{\mathrm{mL}}$
$\displaystyle t=\dfrac{x}{u_{x}}$
$\displaystyle y=\dfrac{1}{2}\left(\dfrac{\mathrm{qV}}{\mathrm{mL}}\right)\left(\dfrac{x}{u_{x}}\right)^{2}$
$\displaystyle \mathrm{V}=\dfrac{2 y m L u_{x}{ }^{2}}{e x^{2}}$
$\displaystyle \mathrm{V}=\dfrac{2 \times 1 \times 10^{-2} \times 9.1 \times 10^{-31} \times 2 \times 10^{-2}\left(3 \times 10^{7}\right)^{2}}{1.6 \times 10^{-19} \times\left(3 \times 10^{-2}\right)^{2}}$
$\displaystyle \mathrm{V}=2275$ Volt
Moving Charges and MagnetismMotion in a Magnetic FieldApplyshort_answermedium
More from Moving Charges and Magnetism
- A 2.0 cm segment of wire, carrying 5.0 A current in positive y-direction lies along y -axis, as shown in the…2024 · asked 3×
- Derive an expression for the magnetic field B, due to a circular coil of N turns, each of radius r carrying…2026 · asked 3×
- Assertion: A proton and an electron enter a uniform magnetic field B with the same momentum p such that p is…2024 · asked 3×
- (i) A particle of mass m and charge q is moving with a velocity v in a magnetic field B as shown in the…2024 · asked 3×
- A 1 cm straight segment of a conductor carrying 1 A current in x direction lies symmetrically at origin of…2025 · asked 3×
- A rectangular loop carries a current of 1 A. A straight long wire carrying 2 A current is kept near the loop…2025 · asked 3×
- Assertion: Two long parallel wires, freely suspended and connected in series to a battery, move apart. Reason…2024 · asked 3×
- A circular coil of 30 turns and radius 8.0 cm carrying a current of 6 A is suspended vertically in a uniform…2026 · asked 3×
CBSE Class 12 Physics past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.