NEB Class 12 Science Physics Question Paper 2080 (Set A)

For the photoelectric effect in sodium, the figure shows the plot of cut-off voltage versus frequency of incident radiation. The threshold frequency is

The moment of momentum is called

The temperature of inversion of a thermocouple is 700°C and the neutral temperature is 365°C. Then, the temperature of cold junction must be

When a gas undergoes adiabatic expansion, its internal energy

Two waves are $y = a\sin(\omega t - kx)$ and $y = a\cos(\omega t - kx)$. Now, the phase difference between the two waves is

The emf of a battery A is balanced by a length of 75 cm on a potentiometer wire. The standard cell of emf 1.02 V is balanced by a length of 50 cm. The emf of a cell is

The efficiency of Carnot's Cycle is independent of

a. An electron and a proton enter in a transverse electric field with the same velocity. Which particle has more curved trajectory? Explain. (2)

b. An electron moving with a speed of $10^7$ m/s is passed into a magnetic field of intensity 0.1 T. What is the radius of the path of the electron inside the field? ($e/m = 1.8\times10^{11}$ C/kg) (3)

a. What do you mean by cyclic process? (1)

b. How the heat and thermodynamic process is useful in our daily life? Explain. (1)

c. A gas in a cylinder is initially at a temperature of 17°C and pressure $1.01\times10^5$ N/m². If it is compressed adiabatically to one-eighth of its original volume, what would be the final temperature and pressure of the gas? (3)

or

a. Spark plug is not necessary in a diesel engine. Why? (2)

b. The figure on the right side represents the PV-diagram of different stages of a thermodynamic process. Calculate the work done in each stage and the net work done in the complete cyclic process. (3)

a. What do you mean by rigid body? (1)

b. How does angular velocity differ from the linear velocity? (1)

c. Derive an expression for the Moment of Inertia of a uniform rod about an axis through its centre and perpendicular to its length. (3)

a. Why the connections between the resistors in a meter bridge are made of thick copper strips? (1)

b. Why is it generally preferred to obtain the balance length near the mid-point of the bridge wire? (1)

c. Calculate the potential difference between the 4Ω resistor in the given electrical circuit. (3)

a. How transverse wave is different from longitudinal wave? (1)

b. Derive the Newton's formula for the velocity of sound. (2)

c. What correction was made by Laplace? Explain. (2)

a. Draw the magnetic field lines for the current carrying solenoid. (1)

b. State and explain the Biot and Savart law. (2)

c. Use this law to calculate the magnetic field at the centre of a current carrying circular coil. (3)

d. A 60 cm long wire of mass 10 gm is suspended horizontally in a transverse magnetic field of flux density 0.4 T through two springs at its two ends. Calculate the current required to pass through the wire so that there is zero tension in the springs. (2)