NEET Physics MCQs

Two resistors with resistances $R_1$ and $R_2$ are connected in series. Derive an expression for the equivalent resistance.

A parallel plate capacitor is being charged by a constant current $I$. The area of the plates is $A$ and the separation is $d$. The displacement current density between the plates is:

A heating coil is rated 220 V and 1000 W. If the coil's operating voltage is reduced by 10% while maintaining a constant current, what is the new power dissipation?

A conductor of cross-sectional area $1 imes 10^{-6} m^2$ carries a current of 4A. If the number density of free electrons is $10^{28} m^{-3}$, and the charge on an electron is $1.6 imes 10^{-19} C$, what is the magnitude of the drift velocity of the electrons, assuming they all contribute to the current?

Two copper wires of equal length but different cross-sectional areas carry the same current. Which of the following statements is true regarding the drift velocities of electrons in the two wires?

A metallic conductor has a current of 5A flowing through it. The free electron density is $8.5 imes 10^{28} m^{-3}$. The cross-sectional area of the conductor is $2 imes 10^{-6} m^2$. If the average relaxation time is $2 imes 10^{-14} s$ and the electric field strength inside the conductor is 2 V/m, what is the mass of an electron (approximately)? (Assume the charge of an electron is $1.6 imes 10^{-19} C$).

Consider a conductor with a non-uniform cross-sectional area. If a steady current flows through it, which of the following quantities remains constant along the length of the conductor?

A cylindrical copper conductor with radius $r_1$ carries a current $I$. If the radius is doubled to $2r_1$ while keeping the current the same, and assuming the electric field within the conductor remains uniform, how does the drift velocity of electrons change?

A potentiometer wire AB is 100 cm long and has a total resistance of 10Ω. It is connected to a driver cell of emf E and internal resistance r. When a cell of emf $E_1$ is balanced against a length of $l_1$, the current through the potentiometer wire is $i_1$. When the cell $E_1$ is shunted by a resistance of 10Ω and balanced against a length $l_2$, the current through the potentiometer wire is $i_2$. Which of the following is true?

A thin wire of length 'L' is bent into a planar loop of irregular shape. A current 'I' flows through it. The loop is placed in a uniform magnetic field 'B' with its plane perpendicular to the field. If the magnetic moment of a circular loop of same perimeter and carrying same current is $\mu_c$, the magnetic moment ($\mu$) of the irregular loop satisfies: