List of top Questions asked in CBSE CLASS XII- 2026

Find ratio \( \left(\frac{\lambda_a}{\lambda_p}\right) \) of the de Broglie wavelength \( \lambda_a \) and \( \lambda_p \) associated respectively with an alpha particle and a proton,
(i) if they are moving with the same kinetic energy.
(ii) just after they are accelerated through the same potential difference.
A heating element using nichrome is connected to a 220 V supply. Initially it draws a current of 2.9 A. After some time, the current attains a steady value of 2.5 A. Find the steady temperature of the heating element if the room temperature is 27 \(^{\circ}\)C. The temperature coefficient of resistance of nichrome is \(1.7 \times 10^{-4}\ ^{\circ}\text{C}^{-1}\).
A 5 cm long pencil is placed along the principal axis of a concave mirror of focal length 20 cm such that its nearest end is at a distance of 25 cm from the mirror. Calculate the length of the image of the pencil.
Assertion (A): On increasing the intensity of incident light of frequency \( v(> v_0) \) on a photosensitive surface, the photocurrent increases. Reason (R): The stopping potential for a photosensitive surface increases with increase of frequency \( v(> v_0) \) of incident light.
In Bohr model, electron transitions from $n=5$ to $n=1$ emit wavelength $\lambda$. What is wavelength for transition $n=5$ to $n=2$?
Assertion (A): On forward biasing a p-n junction diode, the height of the barrier potential increases. Reason (R): In forward biasing of a p-n junction diode, the direction of the applied voltage is in the same direction as the built-in potential.
Assertion (A): Two electric heaters of power \( P_1 \) and \( P_2 (> P_1) \) are joined in series across a dc source of voltage \( V \). The power consumed by the combination will be less than that consumed by \( P_1 \) when connected across the same source. Reason (R): The power consumed by an electric device when connected to a dc source of voltage \( V \) is proportional to its resistance.
An electromagnetic wave is propagating along x-axis. At any instant, the phase difference between the electric field ($\vec{E}$) and magnetic field ($\vec{B}$) is
Assertion (A): Light added to light can produce darkness. Reason (R): When two coherent light waves interfere, there is darkness at position of destructive interference.
Magnetic field due to long wire along y-axis carrying current in -y direction at (50 cm,0,0) points along
The magnetic flux $\phi = 5At^{2} + Bt - 2C$ has SI units of $A$ and $B$ respectively}
The figure shows the variation of capacitive reactance $X_C$ with $1/\omega$ gives two straight lines for capacitors $C_1$ and $C_2$. The ratio $C_1/C_2$ is
A galvanometer of resistance $27\ \Omega$ is converted into an ammeter of range $(0 - 10\text{ mA})$ using a resistance of $3\ \Omega$. The galvanometer will show full scale deflection for a current of about
Which of the following materials has positive and small value of magnetic susceptibility?
A magnet with north pole down is dropped along the axis of a closed solenoid. Observed from top, the induced current is
The maximum kinetic energy of photoelectrons depends on
In Bohr model, for large $n$, spacing between consecutive orbits is proportional to
Three point charges $2q$, $-2q$ and $q$ are kept at the vertices of an equilateral triangle of side $l$. The potential energy of the system is
Two metal spheres of radii $r_1$ and $r_2$ having charges $q_1$ and $q_2$ are brought in contact. Which statement is NOT correct?
A conducting rod of length 50 cm, with one end pivoted, is rotated with angular speed of 60 rpm in a uniform magnetic field of 4.0 mT directed perpendicular to the plane of rotation of rod. Find the emf induced in the rod.
Draw a ray diagram to show the image formation by a concave mirror when the object is kept between its focus and the centre of curvature. Using this diagram, derive the mirror formula.
A concave mirror produces a two times magnified virtual image of an object kept 10 cm in front of it. Calculate the focal length of the mirror.
Draw a labelled diagram of a step-up transformer. State the principle on which it works and obtain the ratio of secondary voltage to primary voltage in terms of number of turns and currents in the two coils.
The ratio of the number of turns in the primary to the secondary of an ideal transformer is \(1:5\). If \(5\) kW power at \(200\) V is supplied to the primary, find
(i) current in the primary, and
(ii) output voltage.
State Faraday’s law of electromagnetic induction.