PUC Science 2nd PUC Class 12 - Karnataka Board PUC Important Questions for Physics

How does drift velocity of electrons in a metallic conductor vary with increase in temperature? Explain.

A cell of emf ‘E’ and internal resistance ‘r’ is connected across a variable resistor ‘R’. Plot a graph showing the variation of terminal potential ‘V’ with resistance R. Predict from the graph the condition under which ‘V’ becomes equal to ‘E’.

Derive an expression for drift velocity of free electrons in a conductor in terms of relaxation time.

Obtain the expression for the cyclotron frequency.

A deuteron and a proton are accelerated by the cyclotron. Can both be accelerated with the same oscillator frequency? Give reason to justify your answer.

Write the expression for the force `vecF` acting on a particle of mass m and charge q moving with velocity `vecV` in a magnetic field `vecB` , Under what conditions will it move in (i) a circular path and (ii) a helical path?

Show that the kinetic energy of the particle moving in a magnetic field remains constant.

A long straight wire of a circular cross-section of radius ‘a’ carries a steady current ‘I’. The current is uniformly distributed across the cross-section. Apply Ampere’s circuital law to calculate the magnetic field at a point ‘r’ in the region for (i) r < a and (ii) r > a.

State the underlying principle of working of a moving coil galvanometer. Write two reasons why a galvanometer can not be used as such to measure current in a given circuit. Name any two factors on which the current sensitivity of a galvanometer depends.

Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why?

Derive the expression for force per unit length between two long straight parallel current carrying conductors. Hence define one ampere.

Explain the principle and working of a cyclotron with the help of a schematic diagram. Write the expression for cyclotron frequency.

Predict the polarity of the capacitor in the situation described below :

Why should the material used for making permanent magnets have high coercivity?

What is the direction of induced currents in metal rings 1 and 2 when current I in the wire is increasing steadily? 

Show diagrammatically how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf induced in the rotating loop.

Define self inductance. Write its S.I. units.

Derive an expression for self inductance of a long solenoid of length l, cross-sectional area A having N number of turns.

Why does current in a steady state not flow in a capacitor connected across a battery? However momentary current does flow during charging or discharging of the capacitor. Explain. 

A series LCR circuit is connected to a source having voltage v = v_m sin ωt. Derive the expression for the instantaneous current I and its phase relationship to the applied voltage.

Obtain the condition for resonance to occur. Define ‘power factor’. State the conditions under which it is (i) maximum and (ii) minimum.